Fix the core of the SAMR access functions. This passes make test, but

usrmgr fails against it. The core of this patch is to move all the
access mask setup into the _samr_OpenXXX functions, and then have
each specific function check the attached access_mask against the
required bits. We can then go through the MS-SAMR doc and match
things up. Signed off by Guenther, and writespace cleanup removal
by Volker.
Jeremy.