fix(launcher): allow afterLaunch to run async scripts

I feel like it's unnecessary. Before, we were checking when the test returns 0 (all test passes), if there are outstanding tasks, we throw an error. However, now with the `deferred.fulfilled()`, protractor would simply hang and never even reach the exit point if we introduced a bug into the launcher/scheduler that's causing not all tests to execute.

Maybe you can think of another case that would make the check necessary?