server/red_worker: introduce {display,cursor}_is_connected
server/red_worker: introduce {display,cursor}_is_connected

Instead of checking for worker->{display,cursor}_channel directly.

alon/spice-server,mathslinux/spice,elmarco/spice,alon/spice-server,fgouget/spice,ya-mouse/spice,mathslinux/spice,mathslinux/spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,mathslinux/spice,alon/spice-server,dezelin/spice,mathslinux/spice,fgouget/spice,dezelin/spice,ya-mouse/spice,elmarco/spice,freedesktop-unofficial-mirror/spice__spice,elmarco/spice,SPICE/spice,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,Fantu/spice,elmarco/spice,SPICE/spice,fgouget/spice,alon/spice-server,alon/spice-server,ya-mouse/spice,Fantu/spice,dezelin/spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,fgouget/spice,dezelin/spice,dezelin/spice,elmarco/spice,freedesktop-unofficial-mirror/spice__spice