MB-10264: added more logging for select_bucket on mccouch socket

Change-Id: Id2930672b2d6c3185970662a4493a8287b29c12b
Reviewed-on: http://review.couchbase.org/33832
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>