[udev] Fix udev iowatch issues

The io watch source id is not cleared when it is going to be implicitly
removed - which can lead to unsuccessful removal attempt when/if
hwal_cleanup() function is called later on.

Clear watch_id when return value from the callback function is going
to cause it to be implicitly removed.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

src/usb_moded-udev.c

@@ -264,8 +264,9 @@ static gboolean monitor_udev(GIOChannel *iochannel G_GNUC_UNUSED, GIOCondition c
 
   release_wakelock(USB_MODED_WAKELOCK_PROCESS_INPUT);
 
-  if (!continue_watching)
+  if (!continue_watching && watch_id )
   {
+    watch_id = 0;
     log_crit("udev io watch disabled");
   }