MB-100 Don't log state after every update_stats message.

The state is just to big. In MB-8231 about 1000 such messages filled
up the log completely.

Change-Id: I0c72ec426a6afda4cb84f1db8cdcb09cc01d72c7
Reviewed-on: http://review.couchbase.org/26231
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>