require cluster.bucket[?].settings permission for /pools/default/buckets
require cluster.bucket[?].settings permission for /pools/default/buckets

...so this api will return 403 if there are no buckets for which
settings can be accessed

Change-Id: I71d8d0e67bc3d916ed8e2f07ad0ed63bbe64a8f8
Reviewed-on: http://review.couchbase.org/60456
Tested-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>
Reviewed-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>

ceejatec/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server