Merge branch 'blackst0ne-rails5-fix-action-cable-mount-path' into 'master'

[Rails5] Fix ActionCable's mount_path configuration

See merge request gitlab-org/gitlab-ce!20051

config/application.rb

@@ -62,7 +62,7 @@ module Gitlab
     # namespaces/users.
     # https://github.com/rails/rails/blob/5-0-stable/actioncable/lib/action_cable.rb#L38
     # Please change this value when configuring ActionCable for real usage.
-    config.action_cable.mount_path = "-" if rails5?
+    config.action_cable.mount_path = "/-/cable" if rails5?
 
     # Configure sensitive parameters which will be filtered from the log file.
     #