str(list_containing_unicode) -> '[ u"..." ]' : the leading u is probably bad for livestatus clients.

let's skip it:

-> First encode unicode to UTF-8 and then use repr(..) on resulting item, one item after each other.
Fix: _has_query() + read_request() was buggy about consecutive queries.

2 requests could be received in one recv() call on the socket (and be stored in our entry of the input buffer list)
then read_request() was returning the 2 requests as only one -> bad/bug.
Give a __str__ to LiveStatusClientThread. for convenience purpose.
Fix: "COMMAND" request doesn't require a response.

Force output to ''.
WaitQuery: Fix: check condition_fulfilled() at first. timeout after.
Don't try to send an empty data.
test: Fix wait_query test according to last change.
Cleaned wait_query.condition_fulfilled():

As condition_fulfilled() is only used to check its bool value then
it's better to return True (on non-empty result) or False.
Enh/Fix: don't try to send an empty response.
docstring