Change HTTPS header check to look for port 443 instead of missing HTTPS environment variable

This fix should act as a workaround for the fact that uhttpd2 has removed HTTPS as a part of the server environment in Barrier Breaker. In order to test:
* Build an image using the bb-test commotion-router branch and including this fix.
* Run through the setup wizard
* Ensure that you can login to the admin interface without issue after setup is complete.

Addresses #440