Adding Two way video and audio streaming test to RtcBot

NOTE: This code review based on this running issue:
https://review.webrtc.org/24939004/

R=andresp@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/25879004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@7498 4adac7df-926f-26a2-2b94-8c16560cd09d