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/firewall_linux.go

@@ -27,14 +27,19 @@ func genKey(format string, input string) string {
 }
 
 // NewFirewall if supported, returns an iptables manager, otherwise returns a nftables manager
-func NewFirewall(parentCTX context.Context) firewallManager {
+func NewFirewall(parentCTX context.Context) (firewallManager, error) {
 	manager, err := newNFTablesManager(parentCTX)
 	if err == nil {
 		log.Debugf("nftables firewall manager will be used")
-		return manager
+		return manager, nil
 	}
-	log.Debugf("fallback to iptables firewall manager: %s", err)
-	return newIptablesManager(parentCTX)
+	fMgr, err := newIptablesManager(parentCTX)
+	if err != nil {
+		log.Debugf("failed to initialize iptables for root mgr: %s", err)
+		return nil, err
+	}
+	log.Debugf("iptables firewall manager will be used")
+	return fMgr, nil
 }
 
 func getInPair(pair routerPair) routerPair {