ipn: rename SetRunExitNode to SetAdvertiseExitNode

From Maisem's code review feedback where he mashed the merge
button by mistake.

Change-Id: I55abce036a6c25dc391250514983125dda10126c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/prefs.go

@@ -446,9 +446,9 @@ func (p *Prefs) AdvertisesExitNode() bool {
 	return v4 && v6
 }
 
-// SetRunExitNode mutates p (if non-nil) to add or remove the two
+// SetAdvertiseExitNode mutates p (if non-nil) to add or remove the two
 // /0 exit node routes.
-func (p *Prefs) SetRunExitNode(runExit bool) {
+func (p *Prefs) SetAdvertiseExitNode(runExit bool) {
 	if p == nil {
 		return
 	}

ipn/prefs_test.go

@@ -659,18 +659,18 @@ func TestPrefsExitNode(t *testing.T) {
 	p.AdvertiseRoutes = []netaddr.IPPrefix{
 		netaddr.MustParseIPPrefix("10.0.0.0/16"),
 	}
-	p.SetRunExitNode(true)
+	p.SetAdvertiseExitNode(true)
 	if got, want := len(p.AdvertiseRoutes), 3; got != want {
 		t.Errorf("routes = %d; want %d", got, want)
 	}
-	p.SetRunExitNode(true)
+	p.SetAdvertiseExitNode(true)
 	if got, want := len(p.AdvertiseRoutes), 3; got != want {
 		t.Errorf("routes = %d; want %d", got, want)
 	}
 	if !p.AdvertisesExitNode() {
 		t.Errorf("not advertising after enable")
 	}
-	p.SetRunExitNode(false)
+	p.SetAdvertiseExitNode(false)
 	if p.AdvertisesExitNode() {
 		t.Errorf("advertising after disable")
 	}