libafs: Fix compile errors in afs_nfsclnt.c

libafs: Fix compile errors in afs_nfsclnt.c

 - tokenUnion is a union, not a struct

 - 'struct rxkadToken' typo

 - 'tokenPtr' not 'tokenptr'

Change-Id: I7e0fa4f2d34ba4bd68345e9625f40d1d7301411e
Reviewed-on: http://gerrit.openafs.org/2764
Tested-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Reviewed-by: Derrick Brashear <shadow@dementia.org>