Fixing crash during TLS connection shutdown.

A crash was caused by an incorrect timer handler nxt_h1p_idle_timeout() if
SSL_shutdown() returned SSL_ERROR_WANT_READ/SSL_ERROR_WANT_WRITE.

The flag SSL_RECEIVED_SHUTDOWN is used to avoid getting SSL_ERROR_WANT_READ, so
the server won't wait for a close notification from a client.

For SSL_ERROR_WANT_WRITE, a correct timer handler is set up.

src/nxt_router.c

@@ -2477,6 +2477,7 @@ nxt_router_tls_rpc_handler(nxt_task_t *task, nxt_port_recv_msg_t *msg,
             goto fail;
         }
 
+        tlscf->no_wait_shutdown = 1;
         rpc->socket_conf->tls = tlscf;
 
     } else {