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/rule.go

@@ -0,0 +1,41 @@
+package netlink
+
+import (
+	"fmt"
+	"net"
+)
+
+// Rule represents a netlink rule.
+type Rule struct {
+	Priority          int
+	Family            int
+	Table             int
+	Mark              int
+	Mask              int
+	TunID             uint
+	Goto              int
+	Src               *net.IPNet
+	Dst               *net.IPNet
+	Flow              int
+	IifName           string
+	OifName           string
+	SuppressIfgroup   int
+	SuppressPrefixlen int
+}
+
+func (r Rule) String() string {
+	return fmt.Sprintf("ip rule %d: from %s table %d", r.Priority, r.Src, r.Table)
+}
+
+// NewRule return empty rules.
+func NewRule() *Rule {
+	return &Rule{
+		SuppressIfgroup:   -1,
+		SuppressPrefixlen: -1,
+		Priority:          -1,
+		Mark:              -1,
+		Mask:              -1,
+		Goto:              -1,
+		Flow:              -1,
+	}
+}