Bug with HTTP POST requests (content type sent twice)

At some point it seems HttpClient started adding content-length to POST requests (I don't think it used to). This resulted in content-length being sent twice, and sometimes broke POST request ntlm relaying 

e.g. in my testing asp.net gives a 500 when content-length is sent twice, and the module would return with an "#{rhost} is not requesting authentication." error