CLEANUP: resolvers: replace all LIST_DELETE with LIST_DEL_INIT

CLEANUP: resolvers: replace all LIST_DELETE with LIST_DEL_INIT

The code as it is uses crossed lists between many elements, and at
many places the code relies on list iterators or emptiness checks,
which does not work with only LIST_DELETE. Further, it is quite
difficult to place debugging code and checks in the current situation,
and gdb is helpless.

This code replaces all LIST_DELETE calls with LIST_DEL_INIT so that
it becomes possible to trust the lists.