ipn/ipnlocal: refactor to unindent a bit

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

ipn/ipnlocal/local.go

@@ -1088,8 +1088,8 @@ func (b *LocalBackend) loadStateLocked(key ipn.StateKey, prefs *ipn.Prefs, legac
 
 	b.logf("using backend prefs")
 	bs, err := b.store.ReadState(key)
-	if err != nil {
-		if errors.Is(err, ipn.ErrStateNotExist) {
+	switch {
+	case errors.Is(err, ipn.ErrStateNotExist):
 		if legacyPath != "" {
 			b.prefs, err = ipn.LoadPrefs(legacyPath)
 			if err != nil {
@@ -1108,7 +1108,7 @@ func (b *LocalBackend) loadStateLocked(key ipn.StateKey, prefs *ipn.Prefs, legac
 			return fmt.Errorf("initMachineKeyLocked: %w", err)
 		}
 		return nil
-		}
+	case err != nil:
 		return fmt.Errorf("store.ReadState(%q): %v", key, err)
 	}
 	b.prefs, err = ipn.PrefsFromBytes(bs, false)