Enable to configure and use the loopback multicast sockets (issue hazelcast/hazelcast#2594).
Update the XML configuration generator and builder, related to issue #2594.
Add unit tests related to the issue #2594.
Fixing the unit test of the multicast loopback mode.
Cleaning the code of the MulticastLoopbackModeTest class according to the recommendations of the Hazelcast's development team.
Resolve conflicts with the master branch
Fixing the style of the code.

According to the errors found by the code style checker, the code of the
multicast loopback feature is fixed.
https://github.com/hazelcast/hazelcast/issues/3567
IllegalMonitorStateException: Current thread is not owner of the lock! in Hibernate support under heavy load
Replaced `map.tryLock` based implementation in `IMapRegionCache.put` with spin loop around atomic operations.
Split Brain Test for Queue
Merge remote-tracking branch 'origin' into fix/queueSplitBrain
made some corrections based on reviews and rebased
started pluggable jcache module implementation
MaxSizePolicy based on how much free memory there is available
Removed System.out
callable's should get serialized before creating the operation because operation can execute locally and change callable state.
fixes #3812
some tests fixed, since they are relying on not serialized runnable
added a serialization exception check, in order to return the exception to the caller
split brain tests for lock and semaphore
test for map merge policy and issue
fix issue is old version of Merger class does not guarantee merge operation is over.
test name changed
refactor for making enterprise cache configurable as onheap/offheap