BUG#50442: MTR check for rpl_sync fails

The test case crashes and recovers the server twice, and while 
recovering InnoDB sets innodb_file_format_check to different
format on second restart. This makes the test case clean up
check to fail.

We fix this by deploying the option "--innodb_file_format_check='ON'"
in slave startup configuration. This makes the innodb_file_format_check
to not change on secod restart.

mysql-test/suite/rpl/t/rpl_sync-slave.opt

---sync-relay-log-info=1 --relay-log-recovery=1
+--sync-relay-log-info=1 --relay-log-recovery=1 --innodb_file_format_check='ON'