RFR: Parallelize checking if a test update is needed

[Erik Helin]

On Mon, 28 Sep 2020 12:30:23 GMT, Robin Westberg <rwestberg at openjdk.org> wrote:

> The current TestBot getPeriodItems implementation can starve the scheduler a bit during startup, ensure that it always
> returns quickly.

Looks good!

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Marked as reviewed by ehelin (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/851