BUG 1853 : Clustered Data Store causes Out of Memory

createSnapshotTransaction was not being set to null which caused
snapshots from being created in the future and thus did not compact
the memory ultimately leading to the JVM running out of memory

Switched to using an InMemorySnapshotstore for test to avoid having
to deal with the file system and adding unneccessary sleeps

Change-Id: I0cb4b219a09a9bc736bd47533888999ee543a4e5
Signed-off-by: Moiz Raja <moraja@cisco.com>
Merge "BUG 1853 : Clustered Data Store causes Out of Memory"