HttpUtils: wget: fix PUT/POST response parsing

Previously, the wget transport would never return the text of the response
that we receive from the server. For example, when uploading a package candidate,
the server normally responds with a list of warnings that affect the package. But
if you used the wget transport, it only returned a response like "OK". This commit
uses the wget option `--output-document` to capture the server response and return
a correct response.