[krbdev.mit.edu #2062] gssapi ftpd bugs with CONTINUE_NEEDED

[Ken Raeburn via RT]

Our ftpd code doesn't cope with a CONTINUE_NEEDED status from 
gss_accept_sec_context.  The wrong variable is checked in at least one 
case.  One message gets sent to the client with the token to be 
returned, and then another message with a different status code is also 
sent.  Probably other things are going wrong too.  I don't think we've 
tested this path before.

The CONTINUE_NEEDED status can be returned under the new CFX support if 
a context establishment token is received with an unrecognized TOK_ID 
value.  The test code I've set up for CFX can exercise this path when 
compiled in.

Ken