Fix H302 rule after release of oslo.concurrency 0.3.0

'oslo' namespace was removed from oslo.concurency lib and it is now
oslo_concurrency.
Make appropriate change to usage of 'processutils' from oslo concurrency lib
to satisfy pep rule H302.

Change-Id: Ia177c3a1245e5ff33b44216b6d64155d43acba2a