homed: rename home_setup_undo() → home_setup_done()

homed: rename home_setup_undo() → home_setup_done()

This function is a destructor, hence it should be named like one.

(We usually use xyz_free() for a destructor that frees the object passed
itself. xyz_unref() we typically use for destructors that are similar,
but ref counted. xyz_done() usually is used for destructors which free
the members of an object, but not the object itself – to allow stack
allocation of objects. We don't strictly follow this, but it's good to
stick to rules wherever we can.)

No actual code change, just renaming.