Handle missed webhoooks for finished builds #388
Description
Sometimes a try/auto build can finish, but the webhook notification doesn't arrive at bors (rust-lang/rust#144425 (comment)). In that case the build should be correctly time outed after a few hours, but that is not ideal if it actually finished green.
When we check for timeouted builds, it would be nice to also check all pending builds, and if they are finished, then run the normal logic for finishing the build. We need to ensure that it won't race with the command handlers though.