Make IpClientIntegrationTest pass on rvc-dev. am: 097a6d2e am: 999840ca...

        mPacketReaderThread.start();

        mHandler = mPacketReaderThread.getThreadHandler();

        mTapFd = iface.getFileDescriptor().getFileDescriptor();

        // Detach the FileDescriptor from the ParcelFileDescriptor.

        // Otherwise, the garbage collector might call the ParcelFileDescriptor's finalizer, which

        // closes the FileDescriptor and destroys our tap interface. An alternative would be to

        // make the ParcelFileDescriptor or the TestNetworkInterface a class member so they never

        // go out of scope.

        mTapFd = new FileDescriptor();

        mTapFd.setInt$(iface.getFileDescriptor().detachFd());

        mPacketReader = new TapPacketReader(mHandler, mTapFd, DATA_BUFFER_LEN);

        mHandler.post(() -> mPacketReader.start());

    }