Have the view hold a weakref until all external references are removed

Have the view hold a weakref until all external references are removed
so that cleanup can all be done in dns_view_weakattach().

(cherry picked from commit be8af3afb711a04ac140b1debce3b950922d714f)
(cherry picked from commit e3946327035832ec03c064410e5c6881841f8f6f)