Allow threads 60 seconds to exit before being forceful

Right now the fio status thread can sit forever waiting for jobs
to exit, when ctrl-c (or another signal) is sent. Be a bit more
brutal and force quit jobs if they haven't exited on their own
in 60 seconds. That should be long enough to ensure that they
are stuck in some way.

Signed-off-by: Jens Axboe <axboe@fb.com>