Mock qemu calls in sheepdog tests
Mock qemu calls in sheepdog tests

Unit tests for the sheepdog driver were creating temp files
and trying to run qemu-img commands on them. These needied
to be mocked out to not actually make calls.

Change-Id: I3c578f06bbcd344615e436d19da85d46468446b2

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