Add CHECKPOINT_REQUESTED flag to the log message in LogCheckpointStart()

Hi,

I have noticed that the CHECKPOINT_REQUESTED flag information is not
present in the log message of LogCheckpointStart() function. I would
like to understand if it was missed or left intentionally. The log
message describes all the possible checkpoint flags except
CHECKPOINT_REQUESTED flag. I feel we should support this. Thoughts?

Please find the patch attached.

Thanks & Regards,
Nitin Jadhav