MirrorMaker should not clear filtered configs on target topics

If you set additional configurations on a remote topic, MirrorMaker will clear them when it syncs topic configurations.

The issue is that it also clears topic configurations that are filtered. For example this prevents running Cruise Control on the target cluster as it may set follower.replication.throttled.replicas and leader.replication.throttled.replicas.

MirrorMaker should not clear topic configurations that are filtered on the target cluster.