This change fixes the `sed: can't create temp file '/etc/supervisor/supervisord.confXXXXXX': Permission denied` issue when editing the supervisord.conf file during runtime as a non-root user.
While editing the config file, Sed creates a temporary file, saves the result and then finally mv the original file with the temporary one. So we need to set the permission for the /etc/supervisor where the temporary file is created.
Change-Id: Ic9c147a9cf0a6ef94adf702e33054edce1828806
155c070837