ptserver: Fix AccessOK -restricted for SYSADMINID

ptserver: Fix AccessOK -restricted for SYSADMINID

According to the documentation, as well as other code paths that check
for -restricted, the -restricted option does not affect members of
system:administrators. Currently, though, AccessOK only bypasses the
-restricted check if the caller is SYSADMINID itself (i.e. localauth).

Fix AccessOK to only do the -restricted checks if the caller is not in
system:administrators, to match the documentation as well as other
ptserver operations.

Reviewed-on: https://gerrit.openafs.org/13373
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 3a8fa4ecd65d5d743fdc573c9f0f261aee2063b6)

Change-Id: I786830efab229a50a521daf3efc624e949475030
Reviewed-on: https://gerrit.openafs.org/13687
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>