Disable WebRtcVideoMediaChannelSimulcastTest.SimulcastSend tests on Win
Disable WebRtcVideoMediaChannelSimulcastTest.SimulcastSend tests on Win

These tests have turned out to be flaky on Windows.

BUG=4135
TBR=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/35669004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: d95435c17ae13670b3a41ee6153a93c5f6eb9118

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