RPCSEC_GSS: krb5 pre-privacy cleanup

 The code this was originally derived from processed wrap and mic tokens using
 the same functions.  This required some contortions, and more would be required
 with the addition of xdr_buf's, so it's better to separate out the two code
 paths.

 In preparation for adding privacy support, remove the last vestiges of the
 old wrap token code.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>