camera2: Fix TotalCaptureResult#getKeys not to return empty list

public abstract class CameraMetadata<TKey> {

    private static final String TAG = "CameraMetadataAb";

    private static final boolean VERBOSE = false;

    private static final boolean VERBOSE = Log.isLoggable(TAG, Log.VERBOSE);

    /**

     * Set a camera metadata field to a value. The field definitions can be

        if (VERBOSE) Log.v(TAG, "getKeysStatic for " + type);

        // TotalCaptureResult does not have any of the keys on it, use CaptureResult instead

        if (type.equals(TotalCaptureResult.class)) {

            type = CaptureResult.class;

        }

        if (filterTags != null) {

            Arrays.sort(filterTags);

        }