[Restify 7] Fix uncaught exceptions triggering route lookups

[mridgway]

Pre-Submission Checklist

• Opened an issue discussing these changes before opening the PR
• Ran the linter and tests via make prepush
• Included comprehensive and convincing tests for changes

Issues

The current uncaughtException handler attempts to do route lookup if a string is thrown. This behavior is undesirable because it prevents the application from handling the exceptions itself (it never makes it to the user's uncaughtException handler.

Changes

This PR adds a check to the route lookup logic which is typically used when calling next('myString'). It bypasses this code if it handling an uncaught exception.

The test demonstrates how this could be triggered before these code changes: throw 'bar'. I also had to add a check for err.name since that would throw another error in the case of a string being passed to the errEvtNameFromError function. I made the default an empty string, but could use some feedback on whether that makes sense or not.

[hekike]

One small comment, thanks for the PR and covering the edge cases!