Revert of Use RtcpPacket to send REMB in RtcpSender

Revert of Use RtcpPacket to send REMB in RtcpSender (patchset #1 id:1 of https://codereview.webrtc.org/1290573004/ )

Reason for revert:
A few bots started failing rtc_unittests after this was commited. Ex https://build.chromium.org/p/client.webrtc/builders/Linux64%20Debug/builds/5048

Original issue's description:
> Use RtcpPacket to send REMB in RtcpSender
>
> BUG=webrtc:2450
> R=asapersson@webrtc.org
>
> Committed: https://chromium.googlesource.com/external/webrtc/+/35ab4baa20a730de71b390008900a16563cbbe8e

TBR=asapersson@webrtc.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:2450
Committed: https://crrev.com/141c5951f4beda868797c2746002a4b1b267ab2a
Cr-Commit-Position: refs/heads/master@{#9723}

[sprang_webrtc, 2015-08-18 11:37:21]

Created Revert of Use RtcpPacket to send REMB in RtcpSender

[commit-bot: I haz the power, 2015-08-18 11:37:25]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1300863002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1300863002/1

[commit-bot: I haz the power, 2015-08-18 11:37:35]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-18 11:37:44]

Patchset 1 (id:??) landed as
https://crrev.com/141c5951f4beda868797c2746002a4b1b267ab2a
Cr-Commit-Position: refs/heads/master@{#9723}

[sprang_webrtc, 2015-08-21 11:21:41]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.webrtc.org/1309723002/ by sprang@webrtc.org.

The reason for reverting is: This wasn't the cause of the breakage.
Re-reverting.
https://code.google.com/p/webrtc/issues/detail?id=4923.