A query SET @@GLOBAL.binlog_format = ... returns an error when NDB is the
default storage. This fails some tests invoking the set binlog_format explicitly.
because the var turns to be read-only.
  
  In the following are files and method to fix if needed.
  
  t/
  ndb_binlog_basic2.test         # here the failure is benign
  rpl_rbr_to_sbr.test            # does not check any ndb features =>           
 
  .                              # => not_ndb_default is enough
  rpl_row_basic_8partition.test  # set binlog_format can be replaced
  rpl_switch_stm_row_mixed.test  # does not check any ndb features =>
  .                              # => not_ndb_default is enough
  
  two more invoking invoke extra/rpl_truncate_helper.test
  
  rpl_truncate_2myisam           # to be fixed with not_ndb_default
  rpl_truncate_3innodb           # same as above
  .                              # because there is a dedicated to ndb .        
 
  .                              # rpl_truncate_7ndb* suit.

Adapting/testing a new implement
--source include/safe_set_to_maybe_ro_var.inc
to avoid abort due to the error using binlog_format as application.