Errors during webserver's startup scrambles the console when running in foreground

When the webserver crashes during startup (e.g. b/c of a configured but missing certificate file), the whole console output is scrambled if `-background` is __not__ used.

Using `defer termbox.Close()` clears the whole screen. There is currently no other solution available, see https://github.com/nsf/termbox-go/issues/233.
Not using `defer termbox.Close()` misses the console's `reset` operation.