srv_log_files_created: A debug flag to ensure that InnoDB redo log
files can only be created once in the server lifetime, and that
after log files have been created, no crash recovery will take place.
recv_scan_log_recs(): Detect the special case where the log consists
of a sole MLOG_CHECKPOINT record, such as immediately after creating
the redo logs.
recv_recovery_from_checkpoint_start(): Skip the recovery message
if the redo log is logically empty.
