Valgrind: Suppress NSS leak in NegotiatingAuthenticatorTest.

BUG=124445
NOTRY=true
TBR=wtc@chromium.org

Review URL: https://codereview.chromium.org/127253002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243451 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243451