tls: fix test certificate to work on macOS 10.15
macOS 10.15 introduced new requirements for certificates to be trusted:
@@ -53,6 +53,7 @@ fn openssl_keys() -> &'static Keys {
[ ext ]\n\
basicConstraints=CA:FALSE,pathlen:0\n\
subjectAltName = @alt_names
+ extendedKeyUsage=serverAuth,clientAuth
[alt_names]
DNS.1 = localhost
",
