fix race on disconnect

between the time we check for `is_open` and the actual disconnect, the
socket could already have been disconnected by another thread (TOCTOU).
Furthermore, the disconnects can race causing a segfault or similar
issue in the asio's internals.

src/TPPSMonitor.cpp

@@ -76,7 +76,7 @@ void TPPSMonitor::operator()() {
             return true;
         });
         for (auto& ClientToKick : TimedOutClients) {
-            ClientToKick->Disconnect("Timeout");
+            Network().DisconnectClient(*ClientToKick, "Timeout");
         }
         TimedOutClients.clear();
         if (C == 0 || mInternalPPS == 0) {