If we detected that Bluetooth devices were setup, show the Bluetooth
menu so that users can easily turn Bluetooth back on.
This is a bit of a hack, as we cannot detect whether there is a
Bluetooth adapter at all when it's disabled, so we cannot tell whether
there were any Bluetooth devices setup, at some point. This state is
saved in the gnome-shell GSettings in the had-bluetooth-devices-setup
key.
Checking whether we saw Bluetooth devices at one point is a good
enough guess of whether there will be some in the future.
https://bugzilla.gnome.org/show_bug.cgi?id=723848
8ceae3b054