Routemgr error handling (#1073)

In case the route management feature is not supported 
then do not create unnecessary firewall and manager instances. 
This can happen if the nftables nor iptables is not available on the host OS.

- Move the error handling to upper layer
- Remove fake, useless implementations of interfaces
- Update go-iptables because In Docker the old version can not 
determine well the path of executable file
- update lib to 0.70

client/internal/routemanager/manager.go

@@ -27,7 +27,7 @@ type DefaultManager struct {
 	stop           context.CancelFunc
 	mux            sync.Mutex
 	clientNetworks map[string]*clientNetwork
-	serverRouter   *serverRouter
+	serverRouter   serverRouter
 	statusRecorder *peer.Status
 	wgInterface    *iface.WGIface
 	pubKey         string
@@ -36,13 +36,17 @@ type DefaultManager struct {
 
 // NewManager returns a new route manager
 func NewManager(ctx context.Context, pubKey string, wgInterface *iface.WGIface, statusRecorder *peer.Status, initialRoutes []*route.Route) *DefaultManager {
-	mCTX, cancel := context.WithCancel(ctx)
+	serverRouter, err := newServerRouter(ctx, wgInterface)
+	if err != nil {
+		log.Errorf("server router is not supported: %s", err)
+	}
 
+	mCTX, cancel := context.WithCancel(ctx)
 	dm := &DefaultManager{
 		ctx:            mCTX,
 		stop:           cancel,
 		clientNetworks: make(map[string]*clientNetwork),
-		serverRouter:   newServerRouter(ctx, wgInterface),
+		serverRouter:   serverRouter,
 		statusRecorder: statusRecorder,
 		wgInterface:    wgInterface,
 		pubKey:         pubKey,
@@ -59,7 +63,9 @@ func NewManager(ctx context.Context, pubKey string, wgInterface *iface.WGIface,
 // Stop stops the manager watchers and clean firewall rules
 func (m *DefaultManager) Stop() {
 	m.stop()
-	m.serverRouter.cleanUp()
+	if m.serverRouter != nil {
+		m.serverRouter.cleanUp()
+	}
 	m.ctx = nil
 }
 
@@ -77,9 +83,12 @@ func (m *DefaultManager) UpdateRoutes(updateSerial uint64, newRoutes []*route.Ro
 
 		m.updateClientNetworks(updateSerial, newClientRoutesIDMap)
 		m.notifier.onNewRoutes(newClientRoutesIDMap)
-		err := m.serverRouter.updateRoutes(newServerRoutesMap)
-		if err != nil {
-			return err
+
+		if m.serverRouter != nil {
+			err := m.serverRouter.updateRoutes(newServerRoutesMap)
+			if err != nil {
+				return err
+			}
 		}
 
 		return nil