spec: mark directories in /var/run as ghosts

spec: mark directories in /var/run as ghosts

We have several directories that are created on the fly, and which
only contain state relevant to a running libvirtd process (all
located in /var/run).  Since the directories are created as needed,
and make no sense without a running libvirtd, we want them deleted
if libvirt is uninstalled.  And in F15 and newer, /var/run is on
tmpfs (forcing us to recreate on the fly); which means that someone
trying to verify a complete rpm will fail if the directory does not
currently exist because libvirtd has not been started since boot.
The solution, then, is to mark the directories as %ghost, so that
rpm knows that we own them and will clean it up if libvirt is
uninstalled, but will no longer create the directory for us at
install, nor complain at verify time if the directory does not exist.

See https://bugzilla.redhat.com/show_bug.cgi?id=656611.

* libvirt.spec.in (%files): Add %ghost to temporary directories
that we don't install, but want cleaned up on libvirt removal.