Zephyr Migration Tool does not parse correctly Creation Dates of Execution and Step Results attachments

Migration tool is wrongly parsing the creation dates of attachments on zephyr execution and step results.

The result is, in the Xray Attachment database table, for each attachment, the creation date will be empty.

This has impact on the date of the evidences on the page of the Test Run. Every time the user opens the Test Run page, the creation date will show the current time.