Send the client a message when calibre ejects the device.

https://www.mobileread.com/forums/showthread.php?p=3993721

src/calibre/devices/smart_device_app/driver.py

@@ -1456,6 +1456,7 @@ def sync_booklists(self, booklists, end_session=True):
     @synchronous('sync_lock')
     def eject(self):
         self._debug()
+        self._call_client('NOOP', {'ejecting': True})
         self._close_device_socket()
 
     @synchronous('sync_lock')