stop listening to udev events when the filesystem gets configured

Otherwise subiquity kicks off probes when there are the inevitable block
device changes during the installation, which is at best useless but
seems to occasionally cause install failures too.

subiquity/server/controllers/filesystem.py

@@ -88,10 +88,13 @@ class FilesystemController(SubiquityController, FilesystemManipulator):
         log.debug("self.ai_data = %s", data)
         self.ai_data = data
 
+    def configured(self):
+        super().configured()
+        self.stop_listening_udev()
+
     @with_context()
     async def apply_autoinstall_config(self, context=None):
         await self._start_task
-        self.stop_listening_udev()
         await self._probe_task.wait()
         self.convert_autoinstall_config(context=context)
         if not self.model.is_root_mounted():