MB-8663 Process replicator doc updates in xdc_replication.

This allows it to avoid restarts when only settings has changed.

Change-Id: Ifa34ca43212e577c048e6cc1f15e2ae586977130
Reviewed-on: http://review.couchbase.org/28183
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>