Temorary fix for a number of replication tests (rpl.rpl_temp_table_mix_row 
rpl.rpl_trunc_temp rpl.rpl_current_user rpl.rpl_gtid_master_promote):

- THD::decide_logging_format() should not assume that mysql.gtid_slave_pos is 
  a non-replicated table. This used to cause unintended behavior for COMMIT 
  statement: replication would switch to row-based, etc.

The question of what should be done when a user issues a statement that
explicitly modifies mysql.gtid_slave_pos table remains open.