NCBC-668: '$HOST' causes parsing error on Memcached buckets

Change-Id: I0f93191772c99bc34c200de34a6bf85163f7190f
Reviewed-on: http://review.couchbase.org/41889
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Jeffry Morris <jeffrymorris@gmail.com>