net: skip failing or flaky TestInterfaces on freebsd-arm

Updates #15262

Change-Id: I3eb1f6f71d6285d039f11ba6a34b8a599a33bf49
Reviewed-on: https://go-review.googlesource.com/21909
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

src/net/interface_test.go

@@ -5,6 +5,7 @@
 package net
 
 import (
+	"internal/testenv"
 	"reflect"
 	"runtime"
 	"testing"
@@ -56,6 +57,10 @@ type routeStats struct {
 }
 
 func TestInterfaces(t *testing.T) {
+	if runtime.GOOS == "freebsd" && runtime.GOARCH == "arm" {
+		// 100% flaky, actually, at least on some FreeBSD versions
+		testenv.SkipFlaky(t, 15262)
+	}
 	ift, err := Interfaces()
 	if err != nil {
 		t.Fatal(err)