WL#6815 Adapt MySQL Cluster to 5.7

 - the ndb_binlog_default_format.test intends to check that
   the binlog_format of mysqld is automatically upgraded to MIXED
   when mysqld is started with binlog_format = STATEMENT, this
   test was broken now when the default binlog_format has been changed
   to ROW.
 - fix test by changing the config to start mysqld
   with binlog_format STATEMENT
 - improve comments in test describing the test purpose

Author: blaudden

mysql-test/suite/ndb_binlog/t/ndb_binlog_default_format.cnf

@@ -20,6 +20,9 @@ ndb-wait-setup=120
 ndb-cluster-connection-pool=3
 ndb-extra-logging=99
 
+# Will be "auto upgraded" to MIXED
+binlog-format=STATEMENT
+
 [ENV]
 NDB_CONNECTSTRING=             @mysql_cluster.1.ndb_connectstring
 MASTER_MYPORT=                 @mysqld.1.1.port

mysql-test/suite/ndb_binlog/t/ndb_binlog_default_format.test

@@ -1,15 +1,22 @@
 --source include/have_ndb.inc
 --source include/not_embedded.inc
 
+# The purpose of this test is to show that the global binlog_format
+# is automatically upgraded to MIXED in case the mysqld is started
+# with STATEMENT
+
 show variables like 'log_bin';
+
+#
+# Check that binlog_format has been auto upgraded to MIXED
+#
 show variables like 'binlog_format';
 
+#
+# Run some basic statements and check how they look in the binlog
+#
 use test;
 create table test.t1 (a int primary key) engine=ndb;
-
 insert into test.t1 values (1);
-
 drop table test.t1;
-
 --source include/show_binlog_events.inc
-