Fix the flaky test TestLeaderElection

The TestLeaderElection is failing sometimes, example:

http://ci.hive.apache.org/blue/organizations/jenkins/hive-precommit/detail/master/2032/tests

http://ci.hive.apache.org/blue/organizations/jenkins/hive-precommit/detail/PR-4995/3/tests

http://ci.hive.apache.org/job/hive-flaky-check/796/

They are failed because of:
java.lang.AssertionError
     at org.apache.hadoop.hive.metastore.leader.TestLeaderElection.testLeaseLeaderElection(TestLeaderElection.java:121)

assertFalse(lockId1 == instance1.getLockId()); 

Lock remains the same, however it's supposed to be changed after a new leader is elected.