pylint: Fix consider-using-dict-items

Pylint 2.9 introduced new checker:
> Emitted when iterating over the keys of a dictionary and accessing the
  value by index lookup. Both the key and value can be accessed by
  iterating using the .items() method of the dictionary instead.

See pylint-dev/pylint#3389

Fixes: #279
Signed-off-by: Stanislav Levin <slev@altlinux.org>

logger/fleet_commander_logger.py

@@ -1187,8 +1187,7 @@ def _preferences_file_updated(self, monitor, fileobj, otherfile, eventType):
                     self.monitored_preferences[path] = prefs
                 else:
                     logger.debug("New preferences loaded. Checking for changes")
-                    for preference in prefs:
-                        value = prefs[preference]
+                    for preference, value in prefs.items():
                         if preference in self.monitored_preferences[path]:
                             prev = self.monitored_preferences[path][preference]
                             logger.debug(