Revert vendor directory to support old golang (GOPATH mode)

gomodule is still in progress to migrate for now, hence multus
team decide to keep vendor directory to support build without
gomodule.

vendor/github.com/vishvananda/netlink/neigh.go

@@ -0,0 +1,23 @@
+package netlink
+
+import (
+	"fmt"
+	"net"
+)
+
+// Neigh represents a link layer neighbor from netlink.
+type Neigh struct {
+	LinkIndex    int
+	Family       int
+	State        int
+	Type         int
+	Flags        int
+	IP           net.IP
+	HardwareAddr net.HardwareAddr
+	LLIPAddr     net.IP //Used in the case of NHRP
+}
+
+// String returns $ip/$hwaddr $label
+func (neigh *Neigh) String() string {
+	return fmt.Sprintf("%s %s", neigh.IP, neigh.HardwareAddr)
+}