network: set 'removing' flag to remembered object

network: set 'removing' flag to remembered object

Previously, if address_remove() or friends called with a temporary
object, the removing flag is assigned to the temporary object, and is
not set to the remembered object. Hence, e.g.
route_is_ready_to_configure() wrongly judge a required address for a
route is (still) ready, hence networkd fails to configure the route.

Fixes #28009.