Update server.go to reduce race condition in test suite

Change the udpErr and tcpErr to close earlier to reduce liklihood
of race condition in test suite where TestClient_Auth, TestClient_Healthcheck,
and TestClient_TcpKeyMatch/returns_ordered_keys_with_secret fail because
the udp address is detected as already being in use.

server/server.go

@@ -132,11 +132,11 @@ func (s *Server) Close() error {
 		return nil
 	}
 	s.disposed = true
+	udpErr := s.conn.Close()
+	tcpErr := s.tcpConn.Close()
 
 	s.store.DisableCleanup()
 	close(s.messageProcessing)
-	udpErr := s.conn.Close()
-	tcpErr := s.tcpConn.Close()
 
 	if udpErr != nil {
 		return udpErr