Disable bogus test in preparation for --harmony-completion.

R=rossberg
BUG=

Review URL: https://codereview.chromium.org/1423753002

Cr-Commit-Position: refs/heads/master@{#31520}

test/mozilla/mozilla.status

@@ -88,6 +88,9 @@
   # Date.prototype is an Object, not a Date
   'ecma/Date/15.9.5': [FAIL],
 
+  # In ES6, the completion value of a 0-iterations loop is 'undefined'.
+  'ecma/Statements/12.6.3-2': [PASS, FAIL],
+
   ##################### SKIPPED TESTS #####################
 
   # This test checks that we behave properly in an out-of-memory