transport: Shutdown server on disablebinary

... and do the real "sharded::stop" in the background. On node shutdown
it needs to pick up all dangling background stopping.

Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>

transport/controller.cc

@@ -185,6 +185,7 @@ future<> controller::stop_server() {
         _ops_sem.broken();
         _listen_addresses.clear();
         co_await do_stop_server();
+        co_await _bg_stops.close();
     }
 }
 
@@ -214,13 +215,15 @@ future<> controller::do_stop_server() {
 
     try {
         co_await unsubscribe_server(server);
-        co_await server.stop();
+        co_await server.invoke_on_all([] (auto& s) { return s.shutdown(); });
     } catch (...) {
         if (!ex) {
             ex = std::current_exception();
         }
     }
 
+    (void)server.stop().finally([s = std::move(cserver), h = _bg_stops.hold()] {});
+
     if (ex) {
         std::rethrow_exception(std::move(ex));
     }

transport/controller.hh

@@ -9,6 +9,7 @@
 #pragma once
 
 #include <seastar/core/semaphore.hh>
+#include <seastar/core/gate.hh>
 #include <seastar/core/sharded.hh>
 #include <seastar/core/future.hh>
 
@@ -35,6 +36,7 @@ class controller : public protocol_server {
     std::vector<socket_address> _listen_addresses;
     std::unique_ptr<sharded<cql_server>> _server;
     semaphore _ops_sem; /* protects start/stop operations on _server */
+    gate _bg_stops;
     bool _stopped = false;
 
     sharded<auth::service>& _auth_service;