Disable PosixDynamicThreadPoolTest.Basic on TSAN.

This test is giving data race errors.

TBR=sadrul@chromium.org, ajwong@chromium.org
NOTRY=true
BUG=305100

Review URL: https://codereview.chromium.org/26462002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227496 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227496