Return 404 for all network operations without network controller.

This will prevent the api from trying to serve network requests in
systems where libnetwork is not enabled, returning 404 responses in any
case.

Signed-off-by: David Calavera <david.calavera@gmail.com>
Upstream-commit: eb982e7c00192c8306f9c420fb469f087c7b161d
Component: engine

components/engine/api/server/server.go

@@ -170,6 +170,7 @@ func (s *Server) makeHTTPHandler(handler httputils.APIFunc) http.HandlerFunc {
 func (s *Server) InitRouters(d *daemon.Daemon) {
 	s.addRouter(local.NewRouter(d))
 	s.addRouter(network.NewRouter(d))
+
 	for _, srv := range s.servers {
 		srv.srv.Handler = s.CreateMux()
 	}