The spec states that the GUID must be sent as a Base64-encoded GUID in
Unicode format. However in the redirection code we read the (correctly
formatted) GUID and convert it to a binary BLOB.
This PR removes the unnecessary conversion which now results in a
correct RDSTLS auth request.
It also removes some dead code in `rdstls_write_data`.
The client tries to connect using RDSTLS only when it has received a
server redirection PDU with LB_PASSWORD_IS_ENCRYPTED flag.
The server exposes RDSTLS on negotiation if it has been configured on settings.
Then authenticates a client using configured credentials from settings:
RedirectionGuid, Username, Domain, Password.