Disable reduced-size RTCP in default config.
Disable reduced-size RTCP in default config.

Verifies that reduced-size isn't configured in WebRtcVideoEngine2
without explicit configuration (which doesn't exist). Also disables REMB
in the default config because it requires reconfiguration.

Adds default-config tests to make sure that they don't contain
parameters that need to be negotiated between clients.

BUG=chromium:497103, webrtc:4745
R=mflodman@webrtc.org, stefan@webrtc.org

Review URL: https://codereview.webrtc.org/1171533002

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#9384}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: d7da120b40f7a8a8357f23cf6b49aa03f67c1cf6

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