Changes

unittest/test_files.TransparentEF_Test: Actually test encoder

In the test_encode_file() method, we should actually test the encoder,
and not the decoder.  I suppose this was a copy+paste mistake at some
point?  In the LinearFixedEF_Test.test_encoder_record we were already
testing the encoder. Just TransparentEF_Test got it wrong...

Change-Id: Id23305a78ab9acd2e006f2b26b72408795844d23