Disable randomly failing tests:

rpl_udf -- Bug#28993 rpl_udf test causes server crash and valgrind
warning in pushbuild
rpl_ndb_circular -- Bug#29233 rpl_ndb_circular fails randomly
ndb_dd_sql_features -- Bug#29102 ndb_dd_sql_features fails in
pushbuild

mysql-test/t/disabled.def

@@ -48,3 +48,6 @@ ndb_partition_error2	 : HF is not sure if the test can work as internded on all
 im_options_set       : Bug#20294: Instance manager tests fail randomly
 im_options_unset     : Bug#20294: Instance manager tests fail randomly
 mysql_upgrade        : Bug#28560 test links to /usr/local/mysql/lib libraries, causes non-determinism and failures on ABI breakage
+rpl_udf              : Bug#28993 rpl_udf test causes server crash and valgrind warning in pushbuild
+rpl_ndb_circular     : Bug#29233 rpl_ndb_circular fails randomly
+ndb_dd_sql_features  : Bug#29102 ndb_dd_sql_features fails in pushbuild