Vt switch fixes

Hi Ray,

I've noticed a couple of issues with the latest gdm code related to vt-switching / the changes to stop the greeter session when it is not necessary.

This is a first round of fixes for issues I've noticed. Unfortunately just to late for 3.30 I see, so these will have to go into 3.30.1 .

Note I'm still seeing some other issues which I plan to debug tomorrow.

Regards,

Hans