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
Merged-In: Ib852b0555f0e20b858f9dd0b16dbd98dbbd22b55
Merged-In: I0c231bdce89474b53603cc15d55787c8c78a809d
(cherry picked from commit fd4eafe8f6)

Change-Id: Idc0e7ea98dbf57e07ee578bc1772c2111af2e563

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

@@ -730,6 +730,11 @@ public class NetworkManagementService extends INetworkManagementService.Stub {
             ActivityManager.getService().notifyCleartextNetwork(uid,
                     HexDump.hexStringToByteArray(hex));
         }
+
+        @Override
+        public int getInterfaceVersion() {
+            return INetdUnsolicitedEventListener.VERSION;
+        }
     }
 
     //