Review and try to fix most annoying repetitive test failures

[rfay]

Is your feature request related to a problem? Please describe.

We have some test failures that we end up retrying over and over again; they waste our time and testing time. See spreadsheet. Let's get rid of the worst ones.

Describe the solution you'd like

• Fix line 5 (TestConfigOverrideDetection) on madOS. This one is an obvious cleanup flaw, and when it fails it leaves a broken testbot.
• Fix line 2 (TestDevListContinuous) on macOS. It shouldn't be hard as it isn't happening on other platforms.
• php-fpm SIGBUS cases failures in TestDdevLogs (Iine 8) and TestDdevRestoreSnapshot (line 4), both only on macOS. Although we don't know how to fix the underlying error with php-fpm, there should be a workaround. (Try again on 502 error???)

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[rfay]

We've made significant progress on this. If we can kill the one in TestConfigOVerrideDetection, the most annoying current remaining one is mkdir /c failed in the windows builds.

[rfay]

This one becomes an ongoing struggle. We've improved a lot of things. My strategy at this point is to try to append test fixes onto the PR where they fail instead of just retrying them multiple times.