Fix few formatting issues in proxied_memcached_clients_pool.

Change-Id: Ia119e729093ddcbef4581d4b22fa22f027f276f7
Reviewed-on: http://review.couchbase.org/36757
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>