config_drive: ensure the search locations are ordered alphabetically

The internal Python implementation for the configured config drive
search locations is not deterministic.

Make it deterministic by using alphabetically sorted order.

In this case, the search order becomes:

  - type: iso, vfat
  - location: cdrom, hdd, partition

Change-Id: I622700c9408d3acee6d44eabfd73c662df7e7cfd
Signed-off-by: Adrian Vladu <avladu@cloudbasesolutions.com>

Author: ader1990

cloudbaseinit/metadata/services/baseconfigdrive.py

@@ -64,6 +64,11 @@ def _preprocess_options(self):
         if self._searched_locations | CD_LOCATIONS != CD_LOCATIONS:
             raise exception.CloudbaseInitException(
                 "Invalid Config Drive locations %s", self._searched_locations)
+        # Note(avladu): sort the order of the searched locations
+        # This is needed to be sure that the order is respected
+        # See: https://github.com/cloudbase/cloudbase-init/issues/200
+        self._searched_types = sorted(self._searched_types)
+        self._searched_locations = sorted(self._searched_locations)
 
     def load(self):
         super(BaseConfigDriveService, self).load()