auth: Return SuperUser identity for localauth

auth: Return SuperUser identity for localauth

The caller expects identity to be populated when we return 1. So for
localauth, give it an identity. Don't set uname, and in fact, move the
uname declaration so that it is clear that it's not used for most of
this function.

Change-Id: I4dcd466b25f578362290ed2fc65b5bd6e23a91e4
Reviewed-on: http://gerrit.openafs.org/3475
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>