Substitute localhost marker in the JSON

This marker might appear since server release 2.5 as part of CCCP

More info:
* http://review.couchbase.org/29996
* http://review.couchbase.org/30067

Change-Id: Ib888ce6985961266532a3561253aa0633505d9c7
Reviewed-on: http://review.couchbase.org/30834
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>