Remove flaky test cases from peerconnection_unittest. The chain of API calls is tested from top to bottom anyway.
Remove flaky test cases from peerconnection_unittest. The chain of API calls is tested from top to bottom anyway.

BUG=3871
R=mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/41879004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8359}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 40fdb8ab9669ee22b2723d154afeeebd44a08b5d

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