RFR 8170732: GssKrb5Client sends non-zero buffer size when qop is "auth"

[Wang Weijun]

Please take a review at

  http://cr.openjdk.java.net/~weijun/8170732/webrev.00/

According to https://tools.ietf.org/html/rfc4752#section-3.1:

   The client then constructs data, with the first octet containing the
   bit-mask specifying the selected security layer, the second through
   fourth octets containing in network byte order the maximum size
   output_message the client is able to receive (which MUST be 0 if the
   client does not support any security layer),

A test is modified to check this case. Please note that when there is no security layer, you cannot call wrap/unwrap anymore.

Thanks
Max