Follow up fix for the log level "everything"

Commit cd6ed82d1ff48f47ad9e33e6322df62896a76ed5 made "EVERYTHING"
map to LOGL_DEBUG but when writing out the configuration the following
would be written:

  logging level all unknown 0x0

This happend because no string was found for the value 0. Address it
by adding a legacy check for 0 and write out the str from the index
0. Currently this is "EVERYTHING".
1 file changed