…gHub#2317)

* Fix bug in StreamTransformer - ending fragment not getting sent

* Add test to verify fix

Before:

```
> ChunkedStream / StreamTransformer
758 OK: output.moveString(s)
OUTPUT: 65 0d 0a 53 6f 6d 65 20 74 65 73 74 20 64 61 74  e..Some test dat
        61 0d 0a                                         a..
792 FAIL: FS_OUTPUT == s
FAIL in `virtual void StreamTest::execute()`
```

After:

```
>> ChunkedStream / StreamTransformer
741 OK: output.moveString(s)
OUTPUT: 65 0d 0a 53 6f 6d 65 20 74 65 73 74 20 64 61 74  e..Some test dat
        61 0d 0a 30 0d 0a 0d 0a                          a..0....
760 OK: FS_OUTPUT == s
```

This reverts commit 84fc04c.