[Sheriff] Temporarily mark test as flaky.

BUG=
TBR=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/145593002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18770 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

test/mjsunit/mjsunit.status

@@ -35,6 +35,9 @@
   # BUG(v8:2921).
   'debug-step-4-in-frame': [PASS, FAIL, SLOW],
 
+  # TODO(hpayer): Investigate.
+  'json2': [PASS, FLAKY],
+
   ##############################################################################
   # Fails.
   'regress/regress-1119': [FAIL],