MB-24543 start default moxi on Spock clusters only if there's a
MB-24543 start default moxi on Spock clusters only if there's a

..."default" bucket with passwordless access

because:
1. we no longer support access to buckets other than "default"
   via default moxi
2. we should not allow access to password protected "default"
   because it is a security hole
3. access to passwordless "default" is supported only for upgraded
   clusters, since it is not allowed to create passwordless users

Change-Id: I079a15f4ea1f79614ac798185b71724b0b214350
Reviewed-on: http://review.couchbase.org/79333
Tested-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>
Reviewed-by: Dave Finlay <7b10a9ed9f70e64c30b07607a671ae61c33f14c8@couchbase.com>

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