KeyboardInterrupt in train_net does not kill all processes.

[omerbrandis]

hi,

pressing ctrl+c during execution of tools/train_net.py does not kill all the spawned processes.
( this later leads to cuda out of memory error on the following re-executions of the train_net ).

:-)
Omer.

[omerbrandis]

happens for dataloaders.NUM_WORKERS = 4.
when NUM_WORKERS = 1 , keyboard interrupt kills all processes.