Try adding the following property in your client: -
jndiProperties.put("jboss.naming.client.connect.options.org.xnio.Options.SASL_POLICY_NOPLAINTEXT", "false");
When moving to integrate with a JAAS login module we need the username and password to be available to pass into the login module for authentication so we need to configure the client to allow the passing of the password as plain - without this the client is trying to only use digest authentication.