xci: scripts: start-new-vm.sh: Add option to clean VM on failure

xci: scripts: start-new-vm.sh: Add option to clean VM on failure

Sometimes we may want to remove the clean VM in case of failure. This
is mostly true for CI tests because developers do not normally have access
to the deployed VMs to debug problems since they can easily recreate the
same environment using this script. If they ever want direct access to
the slaves then that option can easily be turned off and retrigger the
job. In the meantime, this patch allows slaves to free resources when a
job fails instead of keeping the broken tests around.

Change-Id: I07d56661e45fc64e1ec0db7a359522e4ebd2891a
Signed-off-by: Markos Chandras <mchandras@suse.de>