standalone: also cleanup supervisor configuration

destroying instance is supposed to remove these, but when there are
issues removing instances we sometimes have supervisor config left from
previous instances.

Reformating now delete theses after logging the problem.

slapos/slap/standalone.py

@@ -474,7 +474,19 @@ class StandaloneSlapOS(object):
     for part in unknown_partition_set:
       self._logger.debug(
           "removing partition no longer part of format spec %s", part)
+      # remove partition directory
       shutil.rmtree(part)
+      # remove partition supervisor config, if it was not removed cleanly
+      supervisor_conf = os.path.join(
+          self._instance_root,
+          'etc',
+          'supervisord.conf.d',
+          '%s.conf' % os.path.basename(part))
+      if os.path.exists(supervisor_conf):
+        self._logger.info(
+          "removing leftover supervisor config from destroyed partition at %s",
+          supervisor_conf)
+        os.unlink(supervisor_conf)
 
   def supply(self, software_url, computer_guid=None, state="available"):
     """Supply a software, see ISupply.supply