Added support for mixed host key/CA key types (i.e.: RSA host keys signed by ED25519 CAs) (#120).

test/docker/expected_results/openssh_5.6p1_test2.json

@@ -139,6 +139,7 @@
         },
         {
             "algorithm": "ssh-rsa-cert-v01@openssh.com",
+            "ca_algorithm": "ssh-rsa",
             "casize": 1024,
             "keysize": 1024
         }