conformance: Show the Stage to test invariants
conformance: Show the Stage to test invariants

We need to make the Stage set the MAPPED flag on itself if we want to
verify the MAPPED state. That was always the case - it just worked
before because the Stage was shown at least once.

GNOME/clutter,djdeath/clutter-multithreaded,jigpu/clutter,djdeath/clutter-multithreaded,heysion/clutter-clone,GNOME/clutter,djdeath/clutter,dlespiau/clutter,djdeath/clutter,djdeath/clutter-android,rkudiyarov/clutter_osx,nobled/clutter,collects/clutter,GNOME/clutter,Distrotech/clutter,jigpu/clutter,spatulasnout/clutter,Distrotech/clutter,jigpu/clutter,ebassi/clutter,spatulasnout/clutter,jigpu/clutter,heysion/clutter-clone,ebassi/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,kerrickstaley/clutter-vala,ebassi/clutter,jigpu/clutter,Distrotech/clutter,GNOME/clutter,collects/clutter,nobled/clutter,jigpu/clutter,heysion/clutter-clone,ebassi/clutter,collects/clutter,djdeath/clutter,djdeath/clutter-multithreaded,Distrotech/clutter,dlespiau/clutter,GNOME/clutter,collects/clutter,spatulasnout/clutter,kerrickstaley/clutter-vala,rkudiyarov/clutter_osx,djdeath/clutter-android,spatulasnout/clutter,spatulasnout/clutter,Distrotech/clutter,djdeath/clutter-android,djdeath/clutter-android,heysion/clutter-clone,djdeath/clutter,djdeath/clutter,collects/clutter,ebassi/clutter,dlespiau/clutter,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,kerrickstaley/clutter-vala,heysion/clutter-clone,nobled/clutter,djdeath/clutter,Distrotech/clutter