MB-8098: delete ip_start when ip is updated

and vice versa

So that when node is added to cluster and autorenames itself we don't
leave old and invalid ip_start.

Change-Id: I1076a5dd12b4085dcb815ba4cf09fb4b1ce9c1ad
Reviewed-on: http://review.couchbase.org/25667
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>