kill_list cleanup for cases where a kill request is enqueued right before the corresponding job gets popped
make sure lock on kill_list is always released:

everything in the compute() needs extra care to prevent deadlocks
because any exception in it will be caught and the program will go on.
publish kill request even if job is in 'Queued' status:

this is because the job could be in routing right after we polled its state
Merge pull request #275 from levinas/ff

attempt to fix leak in kill_request