When --cert and --key were supplied TLS was only applied to the listener if
exactly one --addr was given. With two or more --addr flags every listener
without an explicit tls:// prefix silently served cleartext HTTP, so adding a
second --addr to an HTTPS server quietly disabled TLS on both.
Now when TLS is configured every listener serves TLS. An individual listener
can be prefixed with http:// to serve unencrypted HTTP on that address, and
tls:// still marks a listener as TLS explicitly. Using a tls:// address
without --cert and --key is now an error instead of silently serving
cleartext with an https:// URL.
Addresses GHSA-mfvx-7rcj-9m5g finding 3.
Nick Craig-Wood
043e58b83c