Fix tethering upstream determination.

Used to use iface names, but on mobile ifaces are multipurpose.
Refined to use ConnectivityService types.
bug:4530116

Change-Id: Iaa632d5f540d27ffff683bd7d94f8004bf422e71

core/java/android/net/ConnectivityManager.java

@@ -163,6 +163,12 @@ public class ConnectivityManager
      */
     public static final String EXTRA_ERRORED_TETHER = "erroredArray";
 
+    /**
+     * The absence of APN..
+     * @hide
+     */
+    public static final int TYPE_NONE        = -1;
+
     /**
      * The Default Mobile data connection.  When active, all data traffic
      * will use this connection by default.