FIx certificate mapping

I was not able to add to the same regular expression because of python2.6 issue :
sre_constants.error: look-behind requires fixed-width pattern

So I made a second check before matching this regular expression :
```
RX_ALTDN = re.compile(r"(?iu)^X509:.*<S>(([A-Z]+=([-\w _@'.()/]+),?)*(?<!berosservice|CERN Root CA|on Authority))$")
```

This fix is now deployed on my private machine