auth.c: Add termination when server disconnects during authentication

When the server is reaches MaxAuthTries it sends disconnect immediately
which was not correctly handled in the libssh client and hanged.
Solves #11

Signed-off-by: Norbert Pocs <npocs@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

src/packet_cb.c

@@ -78,6 +78,8 @@ SSH_PACKET_CALLBACK(ssh_packet_disconnect_callback){
   ssh_socket_close(session->socket);
   session->alive = 0;
   session->session_state = SSH_SESSION_STATE_ERROR;
+  /* correctly handle disconnect during authorization */
+  session->auth.state = SSH_AUTH_STATE_FAILED;
   /* TODO: handle a graceful disconnect */
   return SSH_PACKET_USED;
 }