merge of the netsamlogon caching code from APPLIANCE_HEAD

Merge ... the netsamlogon caching code from APPLIANCE_HEAD
This replaces the universal group caching code (was originally
based on that code).  Only applies to the the RPC code.

One comment: domain local groups don't show up in 'getent group'
that's easy to fix.

Code has been tested against 2k domain but doesn't change anything
with respect to NT4 domains.

netsamlogon caching works pretty much like the universal group
caching code did but has had much more testing and puts winbind
mostly back in sync between branches.
(This used to be commit aac01dc7bc95c20ee21c93f3581e2375d9a894e1)