vm/qvm-block: create xen hotplug state dir

common/qubes_core

@@ -18,6 +18,8 @@ start()
 	# Set permissions to /proc/xen/xenbus, so normal user can use xenstore-read
 	chmod 666 /proc/xen/xenbus
 
+	mkdir -p /var/run/xen-hotplug
+
 	name=$(/usr/bin/xenstore-read name)
 	if ! [ -f /etc/this_is_dvm ] ; then
 		# we don't want to set hostname for DispVM