Report issues as soon as they are found

[marco-c]

Instead of waiting for the whole set of try tasks to finish, we could report issues as soon as they are found. In order to do this, we'd need to change the behavior of the Harbormaster build reporting (we'd report it as finished only at the end of the set of try tasks, instead of when we push).

I was sure we already had an issue for this, but I can't find it.