ipn/ipnlocal: migrate all platforms to controlplane.tailscale.com

Updates #3488

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/ipnlocal/local.go

@@ -1543,24 +1543,17 @@ func (b *LocalBackend) loadStateLocked(key ipn.StateKey, prefs *ipn.Prefs) (err
 		return fmt.Errorf("PrefsFromBytes: %v", err)
 	}
 
-	// On mobile platforms, ignore any old stored preferences for
+	// Ignore any old stored preferences for https://login.tailscale.com
-	// https://login.tailscale.com as the control server that
+	// as the control server that would override the new default of
-	// would override the new default of controlplane.tailscale.com.
+	// controlplane.tailscale.com.
 	// This makes sure that mobile clients go through the new
 	// frontends where we're (2021-10-02) doing battery
 	// optimization work ahead of turning down the old backends.
-	// TODO(bradfitz): make this the default for all platforms
-	// later. But mobile is a relatively small chunk (compared to
-	// Linux, Windows, macOS) and moving mobile early for battery
-	// gains is nice.
-	switch runtime.GOOS {
-	case "android", "ios":
 	if b.prefs != nil && b.prefs.ControlURL != "" &&
 		b.prefs.ControlURL != ipn.DefaultControlURL &&
 		ipn.IsLoginServerSynonym(b.prefs.ControlURL) {
 		b.prefs.ControlURL = ""
 	}
-	}
 
 	b.logf("using backend prefs for %q: %s", key, b.prefs.Pretty())