[libvirt] libvirt-guest.sh bug fixes

[Stefan Bader]

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