OPSMN-4547: Further fine tuning of the initialise "created on" field.
OPSMN-4547: Further fine tuning of the initialise "created on" field.

The script was failing when the primary specimens had more than one
received events. Made the script to pick the received event with
the latest timestamp for initialising the "created on" field.

krishagni/openspecimen,krishagni/openspecimen,krishagni/openspecimen