[libvirt] libvirt-guest.sh bug fixes

Two small changes, before I forget about submitting them... First one affects all environments the same. The list of UIDs which is generated has each element on a separate line. And using quotes in the echo preserves those newlines. However the processing assumes one line per URI and all UIDs separated by spaces. So without dropping the quotes only one guest will get shutdown/suspended. The second change is for Xen environments only. Domain-0 appears in the list of guests and it is a persistent one. So on shutdown, the script tries to stop Domain-0 (which is not working) and then waits the whole timeout for it to stop. -Stefan