HPCC-33043 Ensure blob storage files are completely written before being read

[ghalliday]

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Testing:

[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-33043

Jirabot Action Result:
Assigning user: [email protected]
Workflow Transition To: Merge Pending
Updated PR

[ghalliday]

Tested by changing the default, and running a program that output a persist and then read from it. 1st time it delays, second time there is now delay
@jakesmith probably worth talking this change through. I added the delay here to ensure we catch all occasions. Since I don't expect the value to be very large I think this is likely to be good enough.

[ghalliday]

Possible problems:

• xref hitting files that have just been written, and introducing delays.
• a delay from being able to see the information about a file in eclwatch after it is created.

[jakesmith]

@ghalliday - looks good. I cannot see any issues.

[github-actions]

Jirabot Action Result:
Added fix version: 9.8.44
Workflow Transition: 'Resolve issue'