Fix exit code
Fix exit code

This fixes https://github.com/ms-iot/ntvsiot/issues/104. It also
fixes an issue where the app doesn't exit immediately even after
the deferral->Complete call.

munyirik/node-uwp-wrapper,ms-iot/node-uwp-wrapper,munyirik/node-uwp-wrapper,ms-iot/node-uwp-wrapper