fixes ZEN-9726

Initial implementation for persistent connection to send encrypted message to windows.  Subclassed twisted Agent, HTTP11ClientProtocol, and Request according to the changes found in twisted ticket 3420:  http://twistedmatrix.com/trac/ticket/3420.  Applied the changeset and the additional diffs.  Changed single global Agent to one Agent per RequestSender to send requests in a single persistent connection.  Attach gssclient to RequestSender for encryption/decryption.  Encrypt message before sending and unfortunately decrypt in multiple areas due to multiple Protocols for receiving data.  
pyflakes: RequestNotSent imported, but not used.