CBLT-283:  use short date for ios, android packages

Change-Id: I95ea249f7d0c46d85a9ef1a393eb9b77b52f6d21
Reviewed-on: http://review.couchbase.org/36864
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>