gitlab: Fix registry push error

Seeing the error `unknown blob` which
https://forum.gitlab.com/t/container-registry-unknown-blob/11696/4
suggests is related to the reverse proxy.  Try a reverse proxy setup
just like the main service.

manifests/service/gitlab.pp

@@ -72,7 +72,7 @@ class nest::service::gitlab (
     ;
 
     'registry.gitlab.james.tl':
-      destination => '172.18.0.2:5000',
+      destination => '172.18.0.2:5050',
     ;
   }
 }

templates/gitlab/gitlab.rb.erb

@@ -10,10 +10,10 @@ external_url 'https://gitlab.james.tl'
 nginx['listen_port'] = 80
 nginx['listen_https'] = false
 
-# Enable and expose internal registry service for
-# httpd to reverse proxy and add TLS
-registry_external_url 'http://registry.gitlab.james.tl'
-registry['registry_http_addr'] = '0.0.0.0:5000'
+# Enable and expose internal registry service for proxying
+registry_external_url 'https://registry.gitlab.james.tl'
+registry_nginx['listen_port'] = 5050
+registry_nginx['listen_https'] = false
 
 # Use dark theme by default
 gitlab_rails['gitlab_default_theme'] = 2