MB-100 Cleanup ns_vbucket_mover:update_replication_post_move.

Variables are renamed to actually reflect what they are
doing. Additionally list comprehension filters that had no effect
removed.

Change-Id: Iacadcf420eef755ee1c70d5aa11338a5e479249c
Reviewed-on: http://review.couchbase.org/27327
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>