Implement 'delete' command for interface removal and refactor 'add' command

utils/delDev.go

@@ -0,0 +1,12 @@
+package utils
+
+import "github.com/vishvananda/netlink"
+
+func DelDev(devname string) error {
+	link, err := netlink.LinkByName(devname)
+	if err != nil {
+		return err
+	}
+	netlink.LinkDel(link)
+	return nil
+}