[catalog_manager] optimization in AsyncAddReplicaTask
[catalog_manager] optimization in AsyncAddReplicaTask

Introduced a minor optimization on AsyncAddReplicaTask::SendRequest()
while populating the set of blacklisted candidates for an extra replica.

With this patch, the code iterates over the UUIDs of the peers in the
committed config to populate the set of the blacklisted candidates,
rather than filtering all tablet servers using the IsRaftConfigMember()
utility function.

Change-Id: I1f46ef2e3e3f385f0abc7e02e521e03d47569413
Reviewed-on: http://gerrit.cloudera.org:8080/11429
Reviewed-by: Adar Dembo <866ca730bfc7f544e3ebce604ceeba4879f23df0@cloudera.com>
Tested-by: Kudu Jenkins

InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu