Fixes #10240

From the linked issue:

• We get to the require.Eventually that asserts that the build was canceled
• This times out after 10 seconds
• It appears that the build job never got canceled after 10 seconds
• It also appears that a second build never got created
• We unfortunately appear to be missing cleanup logs in the output, so hard to troubleshoot further.

Based on the above, it looks like a race between runner.Cleanup doing its thing and the require.Eventually asserting that cleanup happened. I don't see a simple way to synchronize between these two actions, so to reduce the likelihood of this happening in future and hoepfully aid future troubleshooting:

• Added a check that the build is running before we cancel it
• Added cleanup output to logs (TODO done)
• Added some checks to the test cleanup logs

I wasn't able to recrate the original failure after running the test 100 times with DB=ci and -race, so while not 100% confident this completely fixes the flake, I'm hopeful at least.