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/nl/syscall.go

@@ -0,0 +1,68 @@
+package nl
+
+// syscall package lack of rule atributes type.
+// Thus there are defined below
+const (
+	FRA_UNSPEC  = iota
+	FRA_DST     /* destination address */
+	FRA_SRC     /* source address */
+	FRA_IIFNAME /* interface name */
+	FRA_GOTO    /* target to jump to (FR_ACT_GOTO) */
+	FRA_UNUSED2
+	FRA_PRIORITY /* priority/preference */
+	FRA_UNUSED3
+	FRA_UNUSED4
+	FRA_UNUSED5
+	FRA_FWMARK /* mark */
+	FRA_FLOW   /* flow/class id */
+	FRA_TUN_ID
+	FRA_SUPPRESS_IFGROUP
+	FRA_SUPPRESS_PREFIXLEN
+	FRA_TABLE  /* Extended table id */
+	FRA_FWMASK /* mask for netfilter mark */
+	FRA_OIFNAME
+)
+
+// ip rule netlink request types
+const (
+	FR_ACT_UNSPEC = iota
+	FR_ACT_TO_TBL /* Pass to fixed table */
+	FR_ACT_GOTO   /* Jump to another rule */
+	FR_ACT_NOP    /* No operation */
+	FR_ACT_RES3
+	FR_ACT_RES4
+	FR_ACT_BLACKHOLE   /* Drop without notification */
+	FR_ACT_UNREACHABLE /* Drop with ENETUNREACH */
+	FR_ACT_PROHIBIT    /* Drop with EACCES */
+)
+
+// socket diags related
+const (
+	SOCK_DIAG_BY_FAMILY = 20         /* linux.sock_diag.h */
+	TCPDIAG_NOCOOKIE    = 0xFFFFFFFF /* TCPDIAG_NOCOOKIE in net/ipv4/tcp_diag.h*/
+)
+
+const (
+	AF_MPLS = 28
+)
+
+const (
+	RTA_NEWDST     = 0x13
+	RTA_ENCAP_TYPE = 0x15
+	RTA_ENCAP      = 0x16
+)
+
+// RTA_ENCAP subtype
+const (
+	MPLS_IPTUNNEL_UNSPEC = iota
+	MPLS_IPTUNNEL_DST
+)
+
+// light weight tunnel encap types
+const (
+	LWTUNNEL_ENCAP_NONE = iota
+	LWTUNNEL_ENCAP_MPLS
+	LWTUNNEL_ENCAP_IP
+	LWTUNNEL_ENCAP_ILA
+	LWTUNNEL_ENCAP_IP6
+)