Binary stream corruption fix

[PRR24]

Addresses gulpjs/gulp#2803

[Daniel-Sh-uq]

Seems related to #351

[phated]

Needs regression tests still

[nicolashenry]

I think that the test should be the same as this test by just removing "encoding: false".

[erikkemperman]

This fix seems "obviously" correct -- somehow this typo sneaked through the whole vetting or there was some merging weirdness. But I don't yet understand why this branch of the code was never reached by the tests. It's been a long time since I looked at this and there's some things I don't recognize (such as a suite of stream backends, is that right?)
It would be good to have a bunch of failing tests in the old (current) situation which this PR then fixes.

[PRR24]

There are currently no e2e binary stream tests. Here is the example of failing test, please add to the most suitable test file.

  it('should not destroy binary file', function (done) {
    var ranBomInputPath = path.join(testConstants.inputBase, './ranbom.bin');
    var ranBomOutputPath = path.join(testConstants.outputBase, './ranbom.bin');

    function assert(files) {
      var srcResult = fs.readFileSync(ranBomInputPath, null);
      var destResult = fs.readFileSync(ranBomOutputPath, null);
      expect(srcResult).toEqual(destResult);
    }

    pipeline(
      [
        vfs.src(ranBomInputPath, { encoding: false, buffer: false }),
        vfs.dest(testConstants.outputBase),
        concatArray(assert),
      ],
      done
    );
  });

[woody-li]

Gentle ping, any progress on this?