Replica which failed to register in Zk can become leader

In case of when an exception is thrown in ZkController.register() a replica can still be able to joinElection and become leader after that. This will cause many problems, one of the problems can happen (the patch including a test which lead to this failure) is

A replica with DOWN state can become a leader and the shard will be stuck in this state forever until the replica is removed or the node contains the replica is restarted.

This won't be a problem in Solr 7.2.1 because a replica with last published state = DOWN can't become a leader, only since SOLR-7034 get resolved (by SOLR-12011)