machine: Only bind name to Topbar.status if current
machine: Only bind name to Topbar.status if current

Just cause the UI state is DISPLAY, doesn't mean every machine should
bind it's name to topbar status. Only current machine should do that.

https://bugzilla.gnome.org/show_bug.cgi?id=754419

vbenes/gnome-boxes,vbenes/gnome-boxes