gitlab: Adjust gitlab-workhorse promise to upstream changes

As gitlab-workhorse is now serving everything, it proxies unknown-to-it
requests to unicorn, and that returns redirect to /users/sign_in for
/non-existent, not 403.

Adjust the promise and just verify whether we can get /static.css

NOTE nginx promise now effectively depends on gitlab-workhorse being up
    and running - because nginx is now configured to be only an SSL
    terminator and all requests processing is done by gitlab-workhorse and
    services below it.

    If in the future we'll need a pure nginx-is-up promise, we can
    introduce something to nginx config and verify that particular http
    endpoint.

/cc @kazuhiko, @jerome

software/gitlab/instance-gitlab.cfg.in

@@ -532,10 +532,7 @@ depend  =
 
 [promise-gitlab-workhorse]
 <= promise-byurl
-# gitlab-workhorse works on repositories. Here we only check it accepts an
-# serves requests, so request is non-existent URL and expected code is 403
-url     = --unix-socket ${gitlab-workhorse:socket}  http:/non-existent
-http_code   = 403
+url     = --unix-socket ${gitlab-workhorse:socket}  http:/static.css
 
 
 # gitlab-workhorse logs to stdout/stderr - logs are handled by slapos not us
@@ -729,6 +726,8 @@ depend  =
 
 [promise-nginx]
 <= promise-byurl
+# XXX this depends on gitlab-workhorse being up
+#     (nginx is configured to proxy all requests to gitlab-workhorse)
 url     = ${backend-info:url}/static.css
 
 [logrotate-entry-nginx]

software/gitlab/software.cfg

@@ -247,7 +247,7 @@ md5sum  = 97b7f5654bc280542ee348cb6fa60893
 
 [instance-gitlab.cfg.in]
 <= download-file
-md5sum  = 0d4b88fdadd315189199b160435bd82e
+md5sum  = dd9dd3e5f7fc22f18f70ee905786c298
 
 [macrolib.cfg.in]
 <= download-file