All the fields in DefaultNetworkSettings were deprecated in Engine v1.9
and scheduled for removal in v17.12. However, they're still return in
all supported API versions.
As we still need to keep backward compatibility for older API versions,
this change leverages the newly added 'compat' package to return these
fields despite being removed from the Go struct.
Signed-off-by: Albin Kerouanton <albinker@gmail.com>