CBLT-283:  if sync_gateway is good, show link to installer

Change-Id: I28511deb4ec3cd7e365eba5ad33b008c0f68f29c
Reviewed-on: http://review.couchbase.org/36819
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>