Instead of taking the first UPnP response we receive and using that to
create port mappings, store all received UPnP responses, sort and
deduplicate them, and then try all of them to obtain an external
address.
Updates #10602
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I783ccb1834834ee2a9ecbae2b16d801f2354302f