Disabling main.query_cache_28249.test since this test fails

sporadically on 5.1. See Bug#12584161.

Test runs successfully on 5.5/trunk, so this changeset will
be null-merged.

mysql-test/t/disabled.def

@@ -12,4 +12,4 @@
 kill                     : Bug#11748945 2008-12-03 HHunger need some changes to be robust enough for pushbuild.
 read_many_rows_innodb    : Bug#11748886 2010-11-15 mattiasj report already exists
 main.log_tables-big      : Bug#11756699 2010-11-15 mattiasj report already exists
-
+query_cache_28249        : Bug#12584161 2011-11-17 joh      fails sporadically in 5.1 only