Add Conflicts=xendomains.service to libvirtd service

On SUSE distros, we promote libvirt and all the libvirt-based
tools. If a user installs libvirt on their SUSE Xen host, then libvirt
should be king and override xendomains.

bsc#1015348
Index: libvirt-3.3.0/daemon/libvirtd.service.in
===================================================================
--- libvirt-3.3.0.orig/daemon/libvirtd.service.in
+++ libvirt-3.3.0/daemon/libvirtd.service.in
@@ -15,6 +15,7 @@ After=apparmor.service
 After=local-fs.target
 After=remote-fs.target
 After=xencommons.service
+Conflicts=xendomains.service
 Documentation=man:libvirtd(8)
 Documentation=http://libvirt.org