Fix for JENKINS-23152

Bulk of the fix is to move the event listener part out of the trigger and only reference the job by name and do a lookup of the job instance by name when needed.
This should let old instances of the jobs and triggers to be removed correctly and not have any duplicates cause trouble.
Yea, but then we would have to wait forever for it to come into an LTS version that we can depend on.
Maybe make a separate library plugin with that feature instead?