HPCC-33147 Add a function to allow keep-alive to be explicitly set

[ghalliday]

Type of change:

• This change is a bug fix (non-breaking change which fixes an issue).
• This change is a new feature (non-breaking change which adds functionality).
• This change improves the code (refactor or other change that does not change the functionality)
• This change fixes warnings (the fix does not alter the functionality or the generated code)
• This change is a breaking change (fix or feature that will cause existing behavior to change).
• This change alters the query API (existing queries will have to be recompiled)

Checklist:

• My code follows the code style of this project.
  • My code does not create any new warnings from compiler, build system, or lint.
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  • I have updated the documentation accordingly, or...
  • I have created a JIRA ticket to update the documentation.
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  • All new and existing tests passed.
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  • Scalability
  • Performance
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  • Premature optimization
  • Existing deployed queries will not be broken
  • This change fixes the problem, not just the symptom
  • The target branch of this pull request is appropriate for such a change.
• There are no similar instances of the same problem that should be addressed
  • I have addressed them here
  • I have raised JIRA issues to address them separately
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Testing:

[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-33147

Jirabot Action Result:
Assigning user: gavin.halliday@lexisnexisrisk.com
Workflow Transition To: Merge Pending
Updated PR

[mckellyln]

Looks good.
Approved.