MB-10594 return 404 for any attempt to use pool other than default

... or 405 if this is DELETE

Change-Id: I300ab59cc4d48e375371a6d8d3b1b3d1b0a36934
Reviewed-on: http://review.couchbase.org/35036
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>