TestNetworkInterface: add support for MacAddress and MTU

Both MacAddress and MTU size are often needed in tests and very painful
to get a hold of without system server permissions.

Test: TH
Change-Id: Ie1a91959916ea39277e76aa1b61f38d59a5d2a90
diff --git a/framework/api/module-lib-current.txt b/framework/api/module-lib-current.txt
index ddac19d..5d776c0 100644
--- a/framework/api/module-lib-current.txt
+++ b/framework/api/module-lib-current.txt
@@ -197,6 +197,8 @@
     method public int describeContents();
     method @NonNull public android.os.ParcelFileDescriptor getFileDescriptor();
     method @NonNull public String getInterfaceName();
+    method @Nullable public android.net.MacAddress getMacAddress();
+    method public int getMtu();
     method public void writeToParcel(@NonNull android.os.Parcel, int);
     field @NonNull public static final android.os.Parcelable.Creator<android.net.TestNetworkInterface> CREATOR;
   }