Additional suppression for TSan deadlock detection

Turns out the one in https://webrtc-codereview.appspot.com/44899004
was not enough to suppress this error.

TBR=pbos@webrtc.org
BUG=4456
TESTED=Passing local TSan run of rtc_unittests

Review URL: https://webrtc-codereview.appspot.com/51479004

Cr-Commit-Position: refs/heads/master@{#8883}
diff --git a/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc b/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc
index b177ba0..d6b24b5 100644
--- a/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc
+++ b/webrtc/build/sanitizers/tsan_suppressions_webrtc.cc
@@ -53,6 +53,7 @@
 "race:webrtc/base/sharedexclusivelock_unittest.cc\n"
 "race:webrtc/base/signalthread_unittest.cc\n"
 // https://code.google.com/p/webrtc/issues/detail?id=4456
+"deadlock:rtc::MessageQueueManager::Clear\n"
 "deadlock:rtc::MessageQueueManager::ClearInternal\n"
 
 // libjingle_p2p_unittest