Revert "Suppress data races in libjingle_peerconnection_unittest"

This reverts commit 8e9c67e6a92b595fa18348e82042f439153321e3.
- https://chromium.googlesource.com/external/webrtc/+/8e9c67e6a92b595fa18348e82042f439153321e3

BUG=4488,4473
TBR=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/47869004

Cr-Original-Commit-Position: refs/heads/master@{#8895}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 65f74a1fc6094fd3cf7eb61982d3a837f1d9ed03