HPCC-31807 Remove stale job queue client entries

[jakesmith]

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Testing:

[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-31807

Jirabot Action Result:
Workflow Transition: Merge Pending
Updated PR

[ghalliday]

@jakesmith approved, but one question just in case it is a potential issue.

[ghalliday]

Could the clearStaleMetaData remove all items, and then a client call this code?

If so, newConnectedCount would be -1.

[jakesmith]

that should never happen.
Dali is only clearing up when it loads, so there should implicitly no clients connected/no SDS connection.
But I've added a guard JIC

[ghalliday]

Great, please squash.

[jakesmith]

Great, please squash.

done.