As per https://github.com/systemd/systemd/blob/v247-rc1/NEWS#L5
there are more kernel uevent types than just "add" and "remove",
and we should be treating everything other than "remove" as being
potentially an "add".

To cope with this, try_add_device() now checks whether the same device
was already added. If so, we ignore it.
Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>