Segment not propgated when subsegment metadata is sufficiently long

The xray-daemon does not propagate a segment to AWS, where metadata is set using `query`, where `query` is both defined and used below:

```python
query="******************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************************"
xray_recorder.begin_segment("segment")
c=xray_recorder.begin_subsegment("foo")
c.put_metadata("bar", query)
xray_recorder.end_subsegment()
xray_recorder.end_segment()
```

`query` is, above, a 882-character long string.

By contrast, if I set `query` to something trivial like `"bla"` then the `xray-daemon` forwards the segment. If I set `query` to a shorter 30-character string like `"******************************"`, then the daemon forwards the segment.

There should be no problem with `query` being very long.

Inizia eseguendo la riproduzione fornita dei metadati del segmento e del sottosegmento con il valore di 882 caratteri, quindi confrontala con il valore di 30 caratteri e con valori banali. Traccia il modo in cui il Python SDK serializza e invia i metadati del sottosegmento allo X-Ray daemon; il lavoro è completato quando il valore lungo dei metadati non impedisce più l'inoltro del segmento.

Scritto dal modello di indicizzazione a partire dal testo della issue.