Adjust negotiation process for pending answer process (#3314)
* add debug statements
* adjust negotiation process
* switch tp simpler proof setLocalDescription()
* fix second race in answer pending state and renegotiation trigger
* revert simpler proof setLocalDescription because of pre SDP munging. I will refactor this in an extra PR
* add state of answer pending process on the second received answer methode as well. Now in any case of receiving answer we take care of this state.
* Clean up pending state in error case