Freeze netd AIDL interface (framework)

This freezes the interface as of the latest beta build, although it has
not changed since then.
This change adds the necessary implementations for getInterfaceVersion.

Test: flashed, WiFi working
Bug: 128803828
Change-Id: I43a6a38685d5fbc669cd573c4d7e7f99bd596952

packages/NetworkStack/src/com/android/server/NetworkObserverRegistry.java

@@ -181,4 +181,9 @@ public class NetworkObserverRegistry extends INetdUnsolicitedEventListener.Stub
 
     @Override
     public void onStrictCleartextDetected(int uid, String hex) {}
+
+    @Override
+    public int getInterfaceVersion() {
+        return INetdUnsolicitedEventListener.VERSION;
+    }
 }

services/core/java/com/android/server/NetworkManagementService.java

@@ -725,6 +725,11 @@ public class NetworkManagementService extends INetworkManagementService.Stub {
             ActivityManager.getService().notifyCleartextNetwork(uid,
                     HexDump.hexStringToByteArray(hex));
         }
+
+        @Override
+        public int getInterfaceVersion() {
+            return INetdUnsolicitedEventListener.VERSION;
+        }
     }
 
     //