refactor: remove superfluous var

conn.shutdown was only set/accessed in handleShutdown, which in turn
is only called on termination of queryLoop and hence multiple
invocations are impossible.

router/connection.go

@@ -269,10 +269,6 @@ func (conn *LocalConnection) handleShutdown() {
 	// (or write elements which are only read by the same
 	// process). Taking locks is only done for elements which are read
 	// by other processes.
-	if conn.shutdown {
-		return
-	}
-	conn.shutdown = true
 
 	if conn.TCPConn != nil {
 		checkWarn(conn.TCPConn.Close())

router/types.go

@@ -60,7 +60,6 @@ type LocalConnection struct {
 	Decryptor     Decryptor
 	Router        *Router
 	UID           uint64
-	shutdown      bool
 	queryChan     chan<- *ConnectionInteraction
 }