Support set test network to tethering upstream

Test: atest EthernetTetheringTest

Change-Id: Ief2a92bc6c573a6bb75c72b7a0630e5c0accfa73

Tethering/common/TetheringLib/src/android/net/ITetheringConnector.aidl

@@ -49,4 +49,6 @@ oneway interface ITetheringConnector {
 
     void stopAllTethering(String callerPkg, String callingAttributionTag,
             IIntResultListener receiver);
+
+    void setPreferTestNetworks(boolean prefer, IIntResultListener listener);
 }

Tethering/common/TetheringLib/src/android/net/TetheringManager.java

@@ -1538,4 +1538,25 @@ public class TetheringManager {
                     }
                 }));
     }
+
+    /**
+     * Whether to treat networks that have TRANSPORT_TEST as Tethering upstreams. The effects of
+     * this method apply to any test networks that are already present on the system.
+     *
+     * @throws SecurityException If the caller doesn't have the NETWORK_SETTINGS permission.
+     * @hide
+     */
+    @RequiresPermission(android.Manifest.permission.NETWORK_SETTINGS)
+    public void setPreferTestNetworks(final boolean prefer) {
+        Log.i(TAG, "setPreferTestNetworks caller: " + mContext.getOpPackageName());
+
+        final RequestDispatcher dispatcher = new RequestDispatcher();
+        final int ret = dispatcher.waitForResult((connector, listener) -> {
+            try {
+                connector.setPreferTestNetworks(prefer, listener);
+            } catch (RemoteException e) {
+                throw new IllegalStateException(e);
+            }
+        });
+    }
 }