Let's be practical and simply destroy (pull the plug on the VM) that
will have its state (snapshot reverted).

Not shutting down (or powering off/destroying) the VM has the side
effect of not reverting the state of the (still running) VM on a
couple of platforms, including EL7.

This fixed issue #396.
Signed-off-by: NCleber Rosa <crosa@redhat.com>