Refresh collectstatic on the settings file

When the settings file changes, the `MEDIA_ROOT` might change which
means the files should be collected again. This also ensures the
settings file has been generated before collection happens.

manifests/config.pp

@@ -27,6 +27,7 @@
       "PULP_SETTINGS=${pulpcore::settings_file}",
     ],
     refreshonly => true,
+    subscribe   => File[$pulpcore::settings_file],
   }
 
 }