The uncaught exception test for `_debugger.js` was not exercising some
code (particularly concerning `interface_.child`) because of the
synchronous nature of the test. This adds an asynchronous version to
increase test coverage.
PR-URL: https://github.com/nodejs/node/pull/8403
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
