tools: Exclude Xen dom0 from libvirt-guests.sh list
tools: Exclude Xen dom0 from libvirt-guests.sh list

With newer versions of libvirt Domain-0 is again visible in the list of
running guests but it should not be considered as a guest for shutdown
or suspend.

Signed-off-by Stefan Bader <stefan.bader@canonical.com>

fabianfreyer/libvirt,eskultety/libvirt,fabianfreyer/libvirt,libvirt/libvirt,zippy2/libvirt,nertpinx/libvirt,jardasgit/libvirt,eskultety/libvirt,VenkatDatta/libvirt,taget/libvirt,taget/libvirt,libvirt/libvirt,crobinso/libvirt,andreabolognani/libvirt,datto/libvirt,nertpinx/libvirt,jardasgit/libvirt,crobinso/libvirt,fabianfreyer/libvirt,datto/libvirt,jardasgit/libvirt,olafhering/libvirt,jfehlig/libvirt,eskultety/libvirt,crobinso/libvirt,taget/libvirt,olafhering/libvirt,libvirt/libvirt,nertpinx/libvirt,libvirt/libvirt,eskultety/libvirt,datto/libvirt,taget/libvirt,datto/libvirt,zippy2/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,datto/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,zippy2/libvirt,taget/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,jfehlig/libvirt,jfehlig/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,eskultety/libvirt,olafhering/libvirt,olafhering/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt