non-deterministic result in the test case for BUG#7947
the bug fix for BUG#7947 now fixed the result of mix_innodb_myisam_binlog test, which
in the past was missing DO RELEASE_LOCK() in the output of SHOW BINLOG EVENTS


mysql-test/r/mix_innodb_myisam_binlog.result:
  DO RELEASE_LOCK() was supposed to be there from the very start
mysql-test/r/rpl_bug7947.result:
  changed select release_lock() to do release_lock() to avoid having to compare the 
  non-deterministic result
mysql-test/t/rpl_bug7947.test:
  changed select release_lock() to do release_lock() to avoid having to compare the 
  non-deterministic result