qa_crowbarsetup.sh: Don't try to start testvm after reboot on Cloud 5.x

The VMs are started meanwhile automatically on reboot, trying to start
them twice doesn't really make a lot of sense.
qa_crowbarsetup: add rsync_iso function

this wraps downloading an iso using a glob specifier
and unpacking its contents
qa_crowbarsetup: use current SLE12 iso
qa_crowbarsetup: make sure to not use the SLE12 iso
Wait for instance to be shut off after "nova stop"

We were rebooting the compute node too fast, and the instance was still
marked as ACTIVE, in the powering-off task state which was never
completed.
Revert "qa_crowbarsetup.sh: Don't try to start testvm after reboot on Cloud 5.x"

This reverts commit 53c4f34b0fc3150e9501498344413cfb12d1d4e2.