Authentication methods are identified by their name, as defined in
[SSH-ARCH]. The "none" method is reserved, and MUST NOT be listed as
supported. However, it MAY be sent by the client. The server MUST
always reject this request, unless the client is to be granted access
without any authentication, in which case, the server MUST accept
this request. The main purpose of sending this request is to get the
list of supported methods from the server.