Don't try to stop libvirt-bin if it's already gone

debian/changelog

+libvirt (1.2.7-5~1.gbpbdae16) UNRELEASED; urgency=medium
+
+  ** SNAPSHOT build @bdae16d287d2739d693bba44382640214bef1dae **
+
+  * [06d457c] Bump comparison version
+    so this applies to current failed upgrades too.
+  * [bdae16d] Remove another obsolete conffile (Closes: #757332)
+
+ -- Guido Günther <agx@sigxcpu.org>  Thu, 07 Aug 2014 12:01:41 +0200
+
 libvirt (1.2.7-4) unstable; urgency=medium
 
   * [5e71896] Move networking configuration to libvirt-daemon-system too

debian/libvirt-daemon-system.preinst

@@ -21,7 +21,7 @@ case "$1" in
 	# trying to restart it again. (Bug: #730604)
 	if dpkg --compare-versions "$2" lt "1.2.7-5~"; then
 	    if [ -d /run/systemd/system ]; then
-	        invoke-rc.d libvirt-bin stop
+	        [ ! -f /lib/systemd/system/libvirt-bin.service ] || invoke-rc.d libvirt-bin stop
 	    fi
 	    # Remove everything we know about libvirt-bin.service
 	    deb-systemd-helper purge libvirt-bin.service >/dev/null