Progress on CR 601

Progress on CR 601

cache the printer_info_2 with the open printer handle.
cache is invalidated on a mod_a_printer() call **on that smbd**.

Yes, this means that the window for admins to step on each other
from different clients just got larger, but since handles a generally
short lived this is probably ok.
(This used to be commit 31272d3b6bb9ec62fd666301c7adfa0c1720a99b)