Disable a few failing NDB tests until they can be investigated

mysql-test/t/disabled.def:
  Disable failing NDB tests

mysql-test/t/disabled.def

 ##############################################################################
 #
-#  List the test cases that are to be disabled temporarely.
+#  List the test cases that are to be disabled temporarily.
 #
 #  Separate the test case name and the comment with ':'.
 #
@@ -15,3 +15,6 @@ rpl_relayrotate : Unstable test case, bug#12429
 rpl_until       : Unstable test case, bug#12429
 rpl_deadlock    : Unstable test case, bug#12429
 kill            : Unstable test case, bug#9712
+ndb_alter_table : Bug #15323
+ndb_cache2      : Bug #15004
+ndb_cache_multi2: Bug #15004