qa_crowbarsetup: Allow bind mounts for local repos

Optionally use local bind mounts instead of nfs when local repositories
should be used.
qa_crowbarsetup: Local repos handling for Cloud

Add local repository support for the cloud iso image.
qa_crowbarsetup: Cleanup repositories

If local repositories are used, cleanup all available repositories so no
remote repos are used.
qa_crowbarsetup: allow for testing of xen

and in theory also other hypervisors
qa_crowbarsetup: do not destory VM

after testsetup. This allows reboot test to work.
fixup! qa_crowbarsetup: do not destory VM
Adjust for cinder multi backend