s3:printing: Do not clear the printer-list.tdb

s3:printing: Do not clear the printer-list.tdb

With the new dcerpc architecture we need to keep printer-list.tdb
around. A spoolss dcerpc call will start rpc-spoolssd which will then
start the background queue process. However in order to enum the
printers we need have a printer-list.tdb. Depending on the number of
printers this task can take several seconds. It is unlinkly that
the printer-list will change all the time, so we might provide outdated
data till it gets refreshed, but this is better than providing no
printer list at all.

If there are a lot of printers, the idle_seconds for the rpc-spoolssd
should be increased so that the background task can finish.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15082

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
(cherry picked from commit 9080cd30d517cb50954e440bb4475c2eeb678906)