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/conntrack_unspecified.go

@@ -0,0 +1,53 @@
+// +build !linux
+
+package netlink
+
+// ConntrackTableType Conntrack table for the netlink operation
+type ConntrackTableType uint8
+
+// InetFamily Family type
+type InetFamily uint8
+
+// ConntrackFlow placeholder
+type ConntrackFlow struct{}
+
+// ConntrackFilter placeholder
+type ConntrackFilter struct{}
+
+// ConntrackTableList returns the flow list of a table of a specific family
+// conntrack -L [table] [options]          List conntrack or expectation table
+func ConntrackTableList(table ConntrackTableType, family InetFamily) ([]*ConntrackFlow, error) {
+	return nil, ErrNotImplemented
+}
+
+// ConntrackTableFlush flushes all the flows of a specified table
+// conntrack -F [table]            Flush table
+// The flush operation applies to all the family types
+func ConntrackTableFlush(table ConntrackTableType) error {
+	return ErrNotImplemented
+}
+
+// ConntrackDeleteFilter deletes entries on the specified table on the base of the filter
+// conntrack -D [table] parameters         Delete conntrack or expectation
+func ConntrackDeleteFilter(table ConntrackTableType, family InetFamily, filter *ConntrackFilter) (uint, error) {
+	return 0, ErrNotImplemented
+}
+
+// ConntrackTableList returns the flow list of a table of a specific family using the netlink handle passed
+// conntrack -L [table] [options]          List conntrack or expectation table
+func (h *Handle) ConntrackTableList(table ConntrackTableType, family InetFamily) ([]*ConntrackFlow, error) {
+	return nil, ErrNotImplemented
+}
+
+// ConntrackTableFlush flushes all the flows of a specified table using the netlink handle passed
+// conntrack -F [table]            Flush table
+// The flush operation applies to all the family types
+func (h *Handle) ConntrackTableFlush(table ConntrackTableType) error {
+	return ErrNotImplemented
+}
+
+// ConntrackDeleteFilter deletes entries on the specified table on the base of the filter using the netlink handle passed
+// conntrack -D [table] parameters         Delete conntrack or expectation
+func (h *Handle) ConntrackDeleteFilter(table ConntrackTableType, family InetFamily, filter *ConntrackFilter) (uint, error) {
+	return 0, ErrNotImplemented
+}