MB-100: wait 5 sec after update_autofailover_settings

Change-Id: I55717170a7b896000d6dbd783d8ade65b0a9ef60
Reviewed-on: http://review.couchbase.org/24925
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>