Set interface for outgoing traffic.

This sets interface for outgoing traffic to the same as for ingoing
(listetning) with libtorrent 1.1.x.

src/base/bittorrent/session.cpp

@@ -1124,6 +1124,7 @@ void Session::configure(libtorrent::settings_pack &settingsPack)
             }
         }
 
+        settingsPack.set_str(libt::settings_pack::outgoing_interfaces, networkInterface().toStdString());
         m_listenInterfaceChanged = false;
     }