MCPorts: Display message if bucket does not exist

Change-Id: I4a19a9879bcc7eb8fe9c10aae3e3002a55beba59
Reviewed-on: http://review.couchbase.org/32616
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>