Fix lint race when not running tests in parallel

[weswigham]

Both runLinterAndComplete and finish were invoking complete (the first when linting was actually done, the second immediately), causing complete to be called for the lint's prerequisite build before the task was actually done (and more times and required), leading to lint running before is prerequisite tsbuild task was complete, resulting in an error if lint rules were not already built.

The jake API isn't exactly forgiving when it comes to ensuring your tasks only complete once when used in the way we've authored; as it turns out, jake supports async tasks returning promises (and if you do so, you no longer have to configure the async flag) - it would be much safer to be using them.

[RyanCavanaugh]

Explains a lot of weirdness. LGTM but why is the node-start project updated in this PR?

[weswigham]

@RyanCavanaugh its reference updates anytime (user) tests are run (or submodules are updated); despite being ignored it gets added by git add . 🤷‍♂️ It doesn't really matter, since we always update the ref to latest before we check it, and it's a pain to purge from the commit once it's been added, since it's not a real file.