ui/console: fix default VC when there are no display

When display is "none", we may still have remote displays (I think it
would be simpler if VNC/Spice were regular display btw). Return the
default VC then, and set them up to fix a regression when using remote
display and it used the TTY instead.

Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1989


Fixes: commit 1bec1cc0 ("ui/console: allow to override the default VC")
Reported-by: German Maglione <gmaglione@redhat.com>
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Thomas Huth <thuth@redhat.com>