Add link to tsan bug to suppression

TBR=machenbach@chromium.org
LOG=n
BUG=none

Review URL: https://codereview.chromium.org/646493002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24487 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

tools/sanitizers/tsan_suppressions.txt

 # Suppressions for TSan v2
 # https://code.google.com/p/thread-sanitizer/wiki/Suppressions
 
-# Deliberate lock cycles in test-lockers
+# Incorrectly detected lock cycles in test-lockers
+# https://code.google.com/p/thread-sanitizer/issues/detail?id=81
 deadlock:LockAndUnlockDifferentIsolatesThread::Run