vendor: switch to using go1.11 modules

vendor/golang.org/x/net/bpf/setter.go

@@ -1,10 +0,0 @@
-// Copyright 2017 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package bpf
-
-// A Setter is a type which can attach a compiled BPF filter to itself.
-type Setter interface {
-	SetBPF(filter []RawInstruction) error
-}