ftl-runner cache has almost 200,000 cached runners

[wesbillman]

When pairing with @mistermoe we saw that he was getting some permission denied on some cached runners so we went to delete the caches and noticed a ton of runner* folders.

I then took a look at my machine and saw ~185,000 similar folders.

[stuartwdouglas]

We had an issue where if your laptop hibernated runner creation could go into a loop with a cancelled context. Adding the max retries stopped the loop, and #3239 should work around the context issue.