Remove psutil dependency
Remove psutil dependency

The version of psutil that was being required is not hosted on
PyPi which caused some issues. This patch removes the psutil
dependency in favor of using the method that was proposed for
the havana backport of polling minimization.

Closes-bug: #1268711
Change-Id: I5a1672cfd195099d92578321153c42b8bfd09b7d

openstack/networking-bigswitch,wolverineav/networking-bigswitch,stackforge/networking-bigswitch,openstack/networking-bigswitch,wolverineav/networking-bigswitch,stackforge/networking-bigswitch