Starting the Keycloak Postgres HA Docker Image fails due to a problem with loading OffilineUserSessions - see stacktrace below.

There is an already resolved?! issue https://issues.jboss.org/browse/KEYCLOAK-1999 filed for Keycloak 1.6.0 that shows some 
workaround suggestions, but I think disabling the support for offline sessions is not a fix to the actual problem...

Would be great to have a real fix, since this hinders the Keycloak Server to start.

Just verified this with:
- jboss/keycloak-ha-postgres:latest
- jboss/keycloak-ha-postgres:1.7.0.Release
- jboss/keycloak-ha-postgres:1.6.1.Release
- jboss/keycloak-ha-postgres:1.6.0.Release

Steps to reproduce:

# Start Postgres Instance:
docker run --name kc-db -e POSTGRES_DATABASE=keycloak -e POSTGRES_USER=keycloak -e POSTGRES_PASSWORD=password -e POSTGRES_ROOT_PASSWORD=password -p 25432:5432 -d postgres

# Start KC Server
docker run --name kc-server1 --link kc-db:postgres -e POSTGRES_DATABASE=keycloak -e POSTGRES_USER=keycloak -e POSTGRES_PASSWORD=password -p 8101:8080 jboss/keycloak-ha-postgres

#Exception during start:
...
10:33:54,461 INFO  [org.jboss.as.clustering.infinispan] (ServerService Thread Pool -- 62) WFLYCLINF0002: Started offlineSessions cache from keycloak container
10:33:54,472 ERROR [org.jboss.msc.service.fail] (ServerService Thread Pool -- 62) MSC000001: Failed to start service jboss.undertow.deployment.default-server.default-host./auth: org.jboss.msc.service.StartException in service jboss.undertow.deployment.default-server.default-host./auth: java.lang.RuntimeException: Failed to construct public org.keycloak.services.resources.KeycloakApplication(javax.servlet.ServletContext,org.jboss.resteasy.core.Dispatcher)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:85)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
at org.jboss.threads.JBossThread.run(JBossThread.java:320)
Caused by: java.lang.RuntimeException: Failed to construct public org.keycloak.services.resources.KeycloakApplication(javax.servlet.ServletContext,org.jboss.resteasy.core.Dispatcher)
at org.jboss.resteasy.core.ConstructorInjectorImpl.construct(ConstructorInjectorImpl.java:160)
at org.jboss.resteasy.spi.ResteasyProviderFactory.createProviderInstance(ResteasyProviderFactory.java:2211)
at org.jboss.resteasy.spi.ResteasyDeployment.createApplication(ResteasyDeployment.java:295)
at org.jboss.resteasy.spi.ResteasyDeployment.start(ResteasyDeployment.java:236)
at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.init(ServletContainerDispatcher.java:112)
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.init(HttpServletDispatcher.java:36)
at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:117)
at org.wildfly.extension.undertow.security.RunAsLifecycleInterceptor.init(RunAsLifecycleInterceptor.java:78)
at io.undertow.servlet.core.LifecyleInterceptorInvocation.proceed(LifecyleInterceptorInvocation.java:103)
at io.undertow.servlet.core.ManagedServlet$DefaultInstanceStrategy.start(ManagedServlet.java:230)
at io.undertow.servlet.core.ManagedServlet.createServlet(ManagedServlet.java:131)
at io.undertow.servlet.core.DeploymentManagerImpl.start(DeploymentManagerImpl.java:511)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentService.startContext(UndertowDeploymentService.java:101)
at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:82)
... 6 more
Caused by: java.lang.NullPointerException
at org.keycloak.models.sessions.infinispan.initializer.OfflineUserSessionLoader.init(OfflineUserSessionLoader.java:25)
at org.keycloak.models.sessions.infinispan.initializer.InfinispanUserSessionInitializer$1.run(InfinispanUserSessionInitializer.java:100)
at org.keycloak.models.utils.KeycloakModelUtils.runJobInTransaction(KeycloakModelUtils.java:244)
at org.keycloak.models.sessions.infinispan.initializer.InfinispanUserSessionInitializer.getOrCreateInitializerState(InfinispanUserSessionInitializer.java:97)
at org.keycloak.models.sessions.infinispan.initializer.InfinispanUserSessionInitializer.startLoading(InfinispanUserSessionInitializer.java:148)
at org.keycloak.models.sessions.infinispan.initializer.InfinispanUserSessionInitializer.loadPersistentSessions(InfinispanUserSessionInitializer.java:78)
at org.keycloak.models.sessions.infinispan.InfinispanUserSessionProviderFactory$3.run(InfinispanUserSessionProviderFactory.java:111)
at org.keycloak.models.utils.KeycloakModelUtils.runJobInTransaction(KeycloakModelUtils.java:244)
at org.keycloak.models.sessions.infinispan.InfinispanUserSessionProviderFactory.loadPersistentSessions(InfinispanUserSessionProviderFactory.java:102)
at org.keycloak.models.sessions.infinispan.InfinispanUserSessionProviderFactory$2.onEvent(InfinispanUserSessionProviderFactory.java:86)
at org.keycloak.services.DefaultKeycloakSessionFactory.publish(DefaultKeycloakSessionFactory.java:47)
at org.keycloak.services.resources.KeycloakApplication.<init>(KeycloakApplication.java:87)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at org.jboss.resteasy.core.ConstructorInjectorImpl.construct(ConstructorInjectorImpl.java:148)
... 19 more

10:33:54,516 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) WFLYCTL0013: Operation ("add") failed - address: ([("deployment" => "keycloak-server.war")]) -