Do not be over-restrictive in the presence of UAC

Do not be over-restrictive in the presence of UAC

We used to explicitly check if a process was UAC-limited and deny all
access to the TGT in that case; however, this makes the MSLSA cache
effectively useless.
Do not try to outsmart UAC, and let it do its own checking -- this allows
UAC-limited access to the MSLSA ccache, which should mean read-write
access to service tickets, and write-only access to the TGT.

Signed-off-by: Kevin Wasserman <kevin.wasserman@painless-security.com>
[kaduk@mit.edu: delete instead of comment out, move comment.]

(cherry picked from commit 8020c64554dd25a4f09df8a28dca924c6ecb5608)

ticket: 7254
status: resolved