pki: Return default RSA key type for DIGEST_AUTO

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
(cherry picked from commit c7628fbfea)

src/pki.c

@@ -214,6 +214,7 @@ ssh_key_signature_to_char(enum ssh_keytypes_e type,
     case SSH_DIGEST_SHA512:
         return "rsa-sha2-512";
     case SSH_DIGEST_SHA1:
+    case SSH_DIGEST_AUTO:
         return "ssh-rsa";
     default:
         return NULL;