Default to exit on failure

[zimmermatt]

Upon discussion, though this seems simple on the surface, there are a
number of nuances that make this tricky to get right. For instance,
if a dependency has a non-daemon thread and the failure occurs in such a
way that a service such as discovery sees the app as in service, the app
could take traffic when it shouldn't.

The main change that occurred since this was put in place was a switch
to primarily use async loggers in the Insight Engineering apps. It was
previously observed that synchronous loggers would emit their logs, even
with the call to System.exit(). Ideally, we can restore that behavior
with async loggers, but that may also prove to not be easy.