Convert mox to mock: tests/compute/test_nova.py
Convert mox to mock: tests/compute/test_nova.py

Replace mox testing library by mock in the file
cinder/tests/compute/test_nova.py

Implements: blueprint mox-to-mock-conversion
Change-Id: Ic819afb4391708a0afebe4fc2855c93e3cb3f4c4

NetApp/cinder,scottdangelo/RemoveVolumeMangerLocks,openstack/cinder,tlakshman26/cinder-https-changes,scality/cinder,JioCloud/cinder,takeshineshiro/cinder,NetApp/cinder,rakeshmi/cinder,tlakshman26/cinder-bug-fix-volume-conversion-full,Hybrid-Cloud/cinder,Nexenta/cinder,bswartz/cinder,tlakshman26/cinder-new-branch,scottdangelo/RemoveVolumeMangerLocks,petrutlucian94/cinder,leilihh/cinder,eharney/cinder,CloudServer/cinder,potsmaster/cinder,rakeshmi/cinder,apporc/cinder,tlakshman26/cinder-new-branch,scality/cinder,nexusriot/cinder,petrutlucian94/cinder,blueboxgroup/cinder,cloudbase/cinder,nikesh-mahalka/cinder,Hybrid-Cloud/cinder,dims/cinder,saeki-masaki/cinder,j-griffith/cinder,potsmaster/cinder,sasukeh/cinder,cloudbase/cinder,ge0rgi/cinder,tlakshman26/cinder-bug-fix-volume-conversion-full,manojhirway/ExistingImagesOnNFS,hguemar/cinder,nexusriot/cinder,saeki-masaki/cinder,bswartz/cinder,winndows/cinder,sasukeh/cinder,Datera/cinder,mahak/cinder,JioCloud/cinder,Nexenta/cinder,Paul-Ezell/cinder-1,manojhirway/ExistingImagesOnNFS,Akrog/cinder,leilihh/cinder,eharney/cinder,julianwang/cinder,blueboxgroup/cinder,winndows/cinder,openstack/cinder,Paul-Ezell/cinder-1,Accelerite/cinder,abusse/cinder,julianwang/cinder,phenoxim/cinder,nikesh-mahalka/cinder,takeshineshiro/cinder,mahak/cinder,Datera/cinder,tlakshman26/cinder-https-changes,CloudServer/cinder,abusse/cinder,Akrog/cinder,duhzecca/cinder,j-griffith/cinder,dims/cinder,phenoxim/cinder,apporc/cinder,hguemar/cinder,Accelerite/cinder,duhzecca/cinder