Improving performance of winbindd_list_groups

[Steven Danneman]

> Looks good to me (reading through)  Have not tested if but
> in theory I can follow the logic and it seems sound.   I'm in
> the ATL airport right now and don't really want to burn
> battery booting VMs for testing.  But I can deal with this
> on Monday if you like.  Or if Volker or someone else has
> already tested it, I'm happy if they wanna check it into
> the v3-3-test branch.
> 

Volker did this ever get checked into v3-3-test?

-Steven