mpd: Change name of output from 'None' to 'Default'

mopidy/frontends/mpd/protocol/audio_output.py

@@ -39,6 +39,6 @@ def outputs(context):
     """
     return [
         ('outputid', 0),
-        ('outputname', None),
+        ('outputname', 'Default'),
         ('outputenabled', 1),
     ]

tests/frontends/mpd/protocol/audio_output_test.py

@@ -15,6 +15,6 @@ class AudioOutputHandlerTest(protocol.BaseTestCase):
     def test_outputs(self):
         self.sendRequest('outputs')
         self.assertInResponse('outputid: 0')
-        self.assertInResponse('outputname: None')
+        self.assertInResponse('outputname: Default')
         self.assertInResponse('outputenabled: 1')
         self.assertInResponse('OK')