Use https and http appropriately when connecting to MusicBrainz

Fixed some bugs:
- MusicBrainz submit URL always has https as protocol: hardcoded, even when
inappropriate. It's just a graphical issue.
- Whipper appears to always communicate with MusicBrainz using musicbrainzngs
over http. The musicbrainzngs.set_hostname(server).
- `musicbrainzngs.set_hostname(server)` always defaults to http. Since musicbrainzngs
version 0.7 the method `set_hostname` takes an optional argument named `use_https`
(defaults to False) which whipper never passes.

Changed behaviour of `server` option (`musicbrainz` section of whipper's configuration file).
Now it expects an URL with a valid scheme (scheme must be `http` or `http`, empty scheme isn't allowed anymore).
Only the scheme and netloc parts of the URL are taken into account.

Fixes #437.

Signed-off-by: JoeLametta <JoeLametta@users.noreply.github.com>

whipper/test/test_common_config.py

@@ -69,25 +69,25 @@ class ConfigTestCase(tcommon.TestCase):
 
     def test_get_musicbrainz_server(self):
         self.assertEqual(self._config.get_musicbrainz_server(),
-                         'musicbrainz.org',
+                         {'scheme': 'https', 'netloc': 'musicbrainz.org'},
                          msg='Default value is correct')
 
         self._config._parser.add_section('musicbrainz')
 
         self._config._parser.set('musicbrainz', 'server',
-                                 '192.168.2.141:5000')
+                                 'http://192.168.2.141:5000')
         self._config.write()
         self.assertEqual(self._config.get_musicbrainz_server(),
-                         '192.168.2.141:5000',
+                         {'scheme': 'http', 'netloc': '192.168.2.141:5000'},
                          msg='Correctly returns user-set value')
 
-        self._config._parser.set('musicbrainz', 'server',
-                                 '192.168.2.141:5000/hello/world')
+        # Test for unsupported scheme
+        self._config._parser.set('musicbrainz', 'server', 'ftp://example.com')
         self._config.write()
         self.assertRaises(KeyError, self._config.get_musicbrainz_server)
 
-        self._config._parser.set('musicbrainz', 'server',
-                                 'http://192.168.2.141:5000')
+        # Test for absent scheme
+        self._config._parser.set('musicbrainz', 'server', 'example.com')
         self._config.write()
         self.assertRaises(KeyError, self._config.get_musicbrainz_server)