After upgrading to the latest release of Waybar the bar will crash
whenever I close the laptop lid. After some debugging I believe it is
because the watching added by watch_name is not being correctly canceled
using unwatch_name. After the Tray object and Host object are destroyed,
additional callbacks will become use-after-free.
Looks like commit 3af1853260 removed the
unwatch_name. I'm not sure why it did that, but it seemed dangerous.
Additionally, bus_name_id_ is created by own_name. According to that
function's documentation, the correct inverse operation is unown_name.
