client/mysqltest.cc:
  Apply Serg's work-around for MySQL BUG#57491.
mysql-test/r/group_commit_binlog_pos.result:
  Accept different ways the server crash is detected.
mysql-test/t/group_commit_binlog_pos.test:
  Accept different ways the server crash is detected.
  Skip in row-based binlogging, as otherwise the binlog offsets will be different.