fix: merges that fail after 2 minutes continue to retry

[ewingjm]

Purpose

Some merges retry for an hour despite the development solution import failing.

Approach

Checks for a value in the completedon field of the importjob rather than checking that the progress field is 100. when determining when to stop polling for updates on the import. Failures occur without the progress being updated to 100.

TODOs

• Automated test coverage for new code
• Documentation updated (if required)
• Build and tests successful