acknowledge when _libssh2_packet_requirev() returns error

when _libssh2_packet_requirev() returns an error when waiting for
SSH_MSG_USERAUTH_SUCCESS or SSH_MSG_USERAUTH_FAILURE, it is an
error and it should be treated as such

src/userauth.c

@@ -136,7 +136,7 @@ static char *userauth_list(LIBSSH2_SESSION *session, const char *username,
                           "Would block requesting userauth list");
             return NULL;
         } else if (rc) {
-            libssh2_error(session, LIBSSH2_ERROR_NONE, "No error");
+            libssh2_error(session, rc, "Failed getting response");
             session->userauth_list_state = libssh2_NB_state_idle;
             return NULL;
         }