SERVER-14135 implement getCurrentMemberState() in LegacyReplicationCoordinator
SERVER-14135 implement canAcceptWritesForDatabase() in LegacyReplicationCoordinator
SERVER-14135 implement shouldIgnoreUniqueIndex() in LegacyReplicationCoordinator
SERVER-14135 implement startReplication() in LegacyReplicationCoordinator
SERVER-13645 rename repl_start to repl_set_seed_list