Commit 8e0a94f1 introduced a post processor that adds an explicit link
between the `HazelcastInstance` and the `EntityManagerFactory` so that
Hazelcast is fully initialized before Hibernate actually kicks in.

Unfortunately, the conditions that were implemented to register this post
processor are wrong and any app that has both JPA and Hazelcast support
blows up if no bean with name `hazelcastInstance` is defined.

This commit fixes the situation and reworks the configuration in a
separate auto-configuration that runs after the Hazelcast and JPA support
and check both the presence of an `EntityManagerFactory` and a bean of
name `hazelcastInstance`. If any of those conditions does not apply the
post processor is no longer registered.

Closes gh-4158