Windows: registry enum do not request write perm

Only Read and Query privileges are required to enumerate the registry
keys, do not request write privileges for an enumeration.

Reviewed-on: http://gerrit.openafs.org/11416
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
(cherry picked from commit fc70e0ddebb8521a69aaeb6e1d249b9ca577db52)

Change-Id: I4c2eba1401a4b3029d40ddc3b18e7ebec73bf943
Reviewed-on: http://gerrit.openafs.org/11420
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>