Clean away use of RtpAudioFeedback interface from RTP/RTCP sender code.

BUG=webrtc:4690

Review URL: https://codereview.webrtc.org/1803923003

Cr-Original-Commit-Position: refs/heads/master@{#12003}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 6021fe2b1e4c7d55cca92ef01cc2750516aa3e9f
13 files changed