Have ipam.ExecDel set CNI_COMMAND to DEL

plugins/main/vlan/vlan.go

@@ -140,6 +140,14 @@ func cmdAdd(args *skel.CmdArgs) error {
 	if err != nil {
 		return err
 	}
+
+	// Invoke ipam del if err to avoid ip leak
+	defer func() {
+		if err != nil {
+			ipam.ExecDel(n.IPAM.Type, args.StdinData)
+		}
+	}()
+
 	// Convert whatever the IPAM result was into the current Result type
 	result, err := current.NewResultFromResult(r)
 	if err != nil {