Fix camera/video activations when changing conference layout.

Fix missing camera button in one-one when video has been deactivated. Test video enabled state on params instead of currentParams in order to know if we are in audio only mode. Add a loading page when conference is not ready or if we are alone in the conference in audio only mode. Remove outgoing call when calling a conference. Fix crash on shutdown. Fix closing window request after calling a conference from smart search bar.