all: rename variables with lowercase-l/uppercase-I

See http://go/no-ell

Signed-off-by: Alex Chan <alexc@tailscale.com>

Updates #cleanup

Change-Id: I8c976b51ce7a60f06315048b1920516129cc1d5d

wgengine/router/osrouter/router_linux_test.go

@@ -870,7 +870,7 @@ func (o *fakeOS) run(args ...string) error {
 		rest = family + " " + strings.Join(args[3:], " ")
 	}
 
-	var l *[]string
+	var ls *[]string
 	switch args[1] {
 	case "link":
 		got := strings.Join(args[2:], " ")
@@ -884,31 +884,31 @@ func (o *fakeOS) run(args ...string) error {
 		}
 		return nil
 	case "addr":
-		l = &o.ips
+		ls = &o.ips
 	case "route":
-		l = &o.routes
+		ls = &o.routes
 	case "rule":
-		l = &o.rules
+		ls = &o.rules
 	default:
 		return unexpected()
 	}
 
 	switch args[2] {
 	case "add":
-		for _, el := range *l {
+		for _, el := range *ls {
 			if el == rest {
 				o.t.Errorf("can't add %q, already present", rest)
 				return errors.New("already exists")
 			}
 		}
-		*l = append(*l, rest)
-		sort.Strings(*l)
+		*ls = append(*ls, rest)
+		sort.Strings(*ls)
 	case "del":
 		found := false
-		for i, el := range *l {
+		for i, el := range *ls {
 			if el == rest {
 				found = true
-				*l = append((*l)[:i], (*l)[i+1:]...)
+				*ls = append((*ls)[:i], (*ls)[i+1:]...)
 				break
 			}
 		}