udevProcessFloppy; remove unnecessary allocation

Use udevHasDeviceProperty instead of udevGetStringProperty.
We do not need to copy the string since we do not need it.

Also add braces around the if body, since the change made
syntax check complain.

src/node_device/node_device_udev.c

@@ -891,17 +891,14 @@ static int udevProcessFloppy(struct udev_device *device,
 {
     int tmp_int = 0;
     int has_media = 0;
-    char *tmp_str = NULL;
 
     if ((udevGetIntProperty(device, "DKD_MEDIA_AVAILABLE",
-                            &tmp_int, 0) == PROPERTY_FOUND))
+                            &tmp_int, 0) == PROPERTY_FOUND)) {
         /* USB floppy */
         has_media = tmp_int;
-    else if (udevGetStringProperty(device, "ID_FS_LABEL",
-                                   &tmp_str) == PROPERTY_FOUND) {
+    } else if (udevHasDeviceProperty(device, "ID_FS_LABEL")) {
         /* Legacy floppy */
         has_media = 1;
-        VIR_FREE(tmp_str);
     }
 
     return udevProcessRemoveableMedia(device, def, has_media);