1) We don't want to restore channels when dbus started, if the
   app is not activated
2) Most importantly, we need an existing window or _ensureRoom fails
   misteriously.
   Previously this would work because it would do:
   startup -> activate -> mainloop -> account manager prepared
   -> ensureRoom -> (-> handle channels -> ensureRoom)
   but in the mission control activation the flow is
   startup -> mainloop -> account manager prepared -> handle channels ->
   ensureRoom -> activate

   We need the second ensureRoom to be effective, and to do so we
   must avoid an ineffective ensureRoom before we handle the channels.

https://bugzilla.gnome.org/show_bug.cgi?id=745499