Fixed a race condition during migration finalization on master node. Also fixes #1317.
Removed recursive writeData() & readData() call blocker code in Operation. It was causing invalid error when multiple threads write the same operation.
Improved backup test.
Added the AsyncAtomicLong and some minor cleanup (e.g. removal of unneeded super calls in constructor)
Merge branch 'feature/3.x/asynclong' of github.com:pveentjer/hazelcast
Merged #1329. Added copyright headers.