gpu_run throws an error even when the job completes successfully

[mdenil]

Avoid this error:

Error in atexit._run_exitfuncs:
Traceback (most recent call last):
  File "/usr/lib64/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/usr/bin/gpu_run", line 23, in _terminate_worker
    os.killpg(worker_pgid, signal.SIGKILL)
OSError: [Errno 3] No such process
Error in sys.exitfunc:
Traceback (most recent call last):
  File "/usr/lib64/python2.7/atexit.py", line 24, in _run_exitfuncs
    func(*targs, **kargs)
  File "/usr/bin/gpu_run", line 23, in _terminate_worker
    os.killpg(worker_pgid, signal.SIGKILL)
OSError: [Errno 3] No such process