fix for issue #3659 by using read and write lock on index store
refactor for issue #3659 by reordering methods have similar logic as closer to themselves
checkstyle fix for issue #3659
second fix attempt for issue #3659
client request and split brain test for countdownLatch
refactor of second fix attempt for issue #3659
3th fix attempt for issue #3659 by using "java.util.concurrent.locks.ReentrantReadWriteLock"
refactor for issue #3659 by reordering methods have similar logic as closer to themselves
osgi: removed com.eclipsesource.json from Import-Packages

com.eclipsesource.json should not appear in the list of
imported packages since it is relocated by the maven
shade plugin as com.hazelcast.com.eclipsesource.json
enhancement for issue #3659 by using "ConcurrentSkipListMap" instead of using "SortedSet" for keys and "ConcurrentMap" for values on SortedIndexStore
checkstyle fix for issue #3659
Merge branch 'master' of https://github.com/hazelcast/hazelcast
Merge branch 'master' of https://github.com/hazelcast/hazelcast
Merge branch 'master' of https://github.com/hazelcast/hazelcast
add delay to expiration times on backups
Merge branch 'master' of https://github.com/hazelcast/hazelcast
fix for issue #3659 by ignoring null values at comparable searches on UnsortedIndexStore
Merge branch 'master' of https://github.com/hazelcast/hazelcast
unit test for issue #3659 about ignoring null values at comparable searches on SortedIndexStore and UnsortedIndexStore
Typographical standardization works