Build takes a long time due to hanging tests and sometimes crash with an OOM.

Failed build with OOM : https://gist.github.com/sebastienblanc/6446997

Successful build with https://github.com/aerogear/aerogear-simplepush-server/blob/master/server-core/src/test/java/org/jboss/aerogear/simplepush/server/datastore/InMemoryDataStoreTest.java#L126 ignored :
>From parent pom : mvn clean install
mvn output : https://gist.github.com/sebastienblanc/6447160