On a non 204 response we parse the HTTP response until complete e.g. do the headers
and body, not just the header. A new interface is added to the response to allow us
to determine the body size so that it may be read out and buffered. The body is
parsed and any error message printed out. In the event that the parsing fails the
raw body is dumped out; better than nothing!
fixes#4411
Signed-off-by: Michael Friedrich <michael.friedrich@icinga.com>