make udev teardown conditional on using udev

test/lib/aux.sh

@@ -62,7 +62,7 @@ prepare_dmeventd() {
 
 teardown_devs() {
 	# Delete any remaining dm/udev semaphores
-	dmsetup udevcomplete_all -y
+	teardown_udev_cookies
 
 	test -n "$PREFIX" && {
 		rm -rf $TESTDIR/dev/$PREFIX*

test/lib/utils.sh

@@ -147,6 +147,12 @@ finish_udev_transaction() {
     fi
 }
 
+teardown_udev_cookies() {
+    if test "$DM_UDEV_SYNCHRONISATION" = 1; then
+	dmsetup udevcomplete_all -y
+    fi
+}
+
 skip() {
     touch SKIP_THIS_TEST
     exit 200