Compare member names in leader identifier and member event instead of by leader ident...

Compare member names in leader identifier and member event instead of by leader identifier contains member name.

ShardManager#markMemberUnavailable/markMemberAvailable now decide whether current leader shards
are on the unavailable/available member by the leader identifier contains the member name.
This way will make a wrong decision when the member name on which leader shard reside contains
the member name which becomes unavailable/available.

New added UT ShardManagerTest#testShardAvailabilityChangeOnMemberWithNameContainedInLeaderIdUnreachable
captures this radical case. And two lines change in ShardManager will pass this UT.

Change-Id: Ib7cd02316c192aeaa8cdac14ff9ece0f872386a6
Signed-off-by: YIN Kangqian <yin.kangqian@zte.com.cn>