Update event filter for asterisk RTPAUDIOQOS events

The suggested event filters on the [Asterisk getting started page](http://adhearsion.com/docs/getting-started/asterisk) didn't work for me on Asterisk 1.8.13.0;  RTPAUDIOQOS* SetVar events continued to come through to Adhearsion.

This patch updates the pattern to something that works on Asterisk 1.8, and I expect on others.