Missing Bugzilla comment with sync PR if server is not reachable at the time of update

If Bugzilla is not reachable at the time the comment will be made for the sync PR the sync bot will not try it again later on. An example can be seen at:

https://bugzilla.mozilla.org/show_bug.cgi?id=1946774#a879740_611017

At that time Bugzilla was failing with a lot of 50x HTTP responses.