Translation job for a translation job

Currently I'm seeing a crash when going to translation jobs because somehow a colleague of mine managed had setup a tranlsation job for a translation job. When this happens the code in Babble_Jobs::user_has_cap() will create a infinite loop.

I will create a pull request to stop it but creating this ticket as a placeholder to find out why this ever happened. Will talk today with him to see how we can reproduce it.

Start at Babble_Jobs::user_has_cap() and reproduce the crash with a translation job configured for another translation job. Trace how the nested job was created and identify the path that causes the infinite loop. Done means the reproduction is understood and the translation-jobs page no longer crashes or loops.

Written by the indexing model from the issue text.