Tests: mock psutil usage in quobyte tests
Tests: mock psutil usage in quobyte tests

Currently, psutil is called here, and the results
depend on the state of the system instead of fixed
mock values.

Closes-Bug: #1675861

Change-Id: Ibff2234d938118c48633667cdc15be5edaf0bd7f

eharney/cinder,phenoxim/cinder,openstack/cinder,openstack/cinder,Datera/cinder,j-griffith/cinder,mahak/cinder,eharney/cinder,mahak/cinder,j-griffith/cinder,phenoxim/cinder,Datera/cinder