Fix it twice

[JohnMcPMS]

Fixes #5365

Change

Fix the issue in two ways:

1. Only use - 1 if supportedConcurrentThreads is greater than 1.
2. Swap the order of setting min and max thread counts on the pool so that setting the minimum thread count to 1 overrides a "bad" allowed thread count of 0 (there are better ways to not do something than creating a thread pool that isn't allowed any threads).

Microsoft Reviewers: Open in CodeFlow