Disable gitlab-shell warning in rake tasks on CE
Whenever running a rake task, if your instance does not have gitlab-shell installed, or is a nightly version and has a master version of shell, you get the following error:
WARNING: This version of GitLab depends on gitlab-shell 7.1.4, but you're running Unknown. Please update gitlab-shell.
This happens a lot in the gitlab cloud native images, as shell only exists in it's own pod, and none of the rails ones.
We should remove this check, or have an option to disable it for our rails images. Having it in there causes confusion when customers are faced with other errors, and having it show up during backup tasks causes concern.