Reset last_sync_error when claiming a job

[wangch079]

Closes https://github.com/elastic/enterprise-search-team/issues/3384

This PR resets last_sync_error, and update status to connected when claiming a job

Checklists

Pre-Review Checklist

• [x] Covered the changes with automated tests
• [x] Tested the changes locally
• [x] Added a label for each target release version (example: v7.13.2, v7.14.0, v8.0.0)
• [x] Considered corresponding documentation changes
• [x] Contributed any configuration settings changes to the configuration reference

[github-actions[bot]]

💔 Failed to create backport PR(s)

The backport operation could not be completed due to the following error: There are no branches to backport to. Aborting.

The backport PRs will be merged automatically after passing CI.

To backport manually run: backport --pr 529 --autoMerge --autoMergeMethod squash