s4:torture: Enforce Printer Class

s4:torture: Enforce Printer Class

Ensure that the provided inf defines Class=Printer for driver installation
to succeed.

Some driver packages(HP Universal Print Driver) include inf files with
other device types such as Class=USB. Attempting to install these will fail
when tested against Windows Server 2016 Print server using
iremotewinspool RPC calls.

Signed-off-by: Justin Stephenson <jstephen@redhat.com>
Reviewed-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Bjoern Jacke <bjacke@samba.org>
Autobuild-User(master): Björn Jacke <bjacke@samba.org>
Autobuild-Date(master): Mon Jan 28 19:34:41 CET 2019 on sn-devel-144