load_broadcaster: Unregister from load_broadcaster::stop_broadcasting

This is in preparation for unregistration returning a future.

Signed-off-by: Rafael Ávila de Espíndola <espindola@scylladb.com>

service/load_broadcaster.hh

@@ -56,13 +56,14 @@ private:
     std::unordered_map<gms::inet_address, double> _load_info;
     timer<> _timer;
     future<> _done = make_ready_future<>();
+    bool _stopped = false;
 
 public:
     load_broadcaster(distributed<database>& db, gms::gossiper& g) : _db(db), _gossiper(g) {
         _gossiper.register_(shared_from_this());
     }
     ~load_broadcaster() {
-        _gossiper.unregister_(shared_from_this());
+        assert(_stopped);
     }
 
     void on_change(gms::inet_address endpoint, gms::application_state state, const gms::versioned_value& value) {

service/misc_services.cc

@@ -130,7 +130,10 @@ void load_broadcaster::start_broadcasting() {
 
 future<> load_broadcaster::stop_broadcasting() {
     _timer.cancel();
-    return std::move(_done);
+    _gossiper.unregister_(shared_from_this());
+    return std::move(_done).then([this] {
+        _stopped = true;
+    });
 }