map: delete map-t device when tearing down map interface

map: delete map-t device when tearing down map interface

Delete the map-t device when tearing down the map-t interface; as such
there's no conflict when the map-t interface comes up again when trying
to add the map-t device as the map-t device was still present
(Can not add: device 'map-wan6_4' already exists!).

Only call ifdown in teardown for map-e and lw6o4 map interfaces types
in order to suppress the trace "wan6_4 (6652): Interface wan6_4_ not found"

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>