Added more tests for Bucket store

Changed bucket store tests to use akka's LocalRefProvider from ClusterRefProvider
to improve performance. Also added more unit tests.

Change-Id: Iadc6b5967074651a99027f10538aee88a7c4ec84
Signed-off-by: Abhishek Kumar <abhishk2@cisco.com>
Changed gossiper test to use akka system's LocalRefProvider

This improves unit test's performance and reliability

Change-Id: I6e669c5994aacb0c6ec3da0a321110572aa29f31
Signed-off-by: Abhishek Kumar <abhishk2@cisco.com>