BUG/MEDIUM: threads/peers: decrement, not increment jobs on quitting

Commit 8d8aa0d ("MEDIUM: threads/listeners: Make listeners thread-safe")
mistakenly placed HA_ATOMIC_ADD(job, 1) to replace a job--, so it maintains
the job count too high preventing the process from cleanly exiting on
reload.

This needs to be backported to 1.8.
1 file changed