CAS 5.1.5 cas_audit no longer written

[atilling]

We're in the process of upgrading to cas 7, but in the meantime we're having a problem with audit logs on our production system. Back in June we updated the log4j.jar file to address a security issue in that version, what we didn't notice at the time is that while all other logging seems to still be running correctly the cas_audit stopped functioning. 

I've tried a few tweaks to the log4j.xml but so far we haven't been able to get this logging to output anymore.