MB-10040: fix in _wait_for_replication_to_catchup

Change-Id: Ifaf53ae318255fc7ba07e26717a982f40f778df4
Reviewed-on: http://review.couchbase.org/32986
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>