Elector's _leadertime is reset when quorum is lost/gained.

_leadertime is reset when elector loses/gains quorum. Hence elector
will not promote/demote any node immediately after it gains quorum.
Elector that just gained quorum will get some more time to know
that if any of the new connected node is master. Unnecessary
failover will be avoided.
Merge pull request #4 from yogarajbaskaravel/koi-fix

Elector's _leadertime is reset when quorum is lost/gained.