Ensure CNode::addrKnown immediately takes little memory when we disconnect the node

src/net.cpp

@@ -556,6 +556,10 @@ void CNode::CloseSocketDisconnect()
             CloseSocket(hSocket);
         }
     }
+    {
+        LOCK(cs_addrKnown);
+        addrKnown.reset();
+    }
 
     // in case this fails, we'll empty the recv buffer when the CNode is deleted
     TRY_LOCK(cs_vRecvMsg, lockRecv);