disconnect the client after the response have been sent. This also happens
if the respons is zero byte long.

In all other cases (unless an error happens), it will now maintain the
connection to allow proper persistant connection testing. This was required
for the NTLM testing to work so I finally had to fix this. Of course most of
the existing HTTP tests will be adjusted to work with this new rule of test
file syntax for HTTP tests.

Also fixed the log function to deal with varargs for better logging.