Merge branch 'pktgen-races'

Oleg Nesterov says:

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net: pktgen: fix race between pktgen_thread_worker() and kthread_stop()

I am not familiar with this code and I have no idea how to test
these changes, so 2/2 comes as a separate change. 1/2 looks like
the obvious bugfix, and probably candidate for -stable.
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Signed-off-by: David S. Miller <davem@davemloft.net>