Fix incorrect rtx config in full_stack tests.
Fix incorrect rtx config in full_stack tests.

BUG=4326
R=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/40819006

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8455}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 343096ac03bfb0e1cadbcead29ce925522c12d5b

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