Fix sending short/long Unicode strings

[afedor]

• Convert to utf8 before writing string so string and string length match

[WollZebra]

Nice finding. Looks good to me.
Did you find a unit test that checks what was written into the stream?
QDataStream &s

[afedor]

That's not very easy since this encoding is only used for some 'metadata', like routing keys and queue names. So if it's not encoded correctly, you end up just not receiving a message at all, since the routing key doesn't match. That's what my test checks