s4/torture: add a leases test with stat open

s4/torture: add a leases test with stat open

This test passes against Windows 2016 but currently fails against Samba
for some reason. The test does the following:

1. A stat open on a file, then
2. a second open with a RWH-lease request

Windows grants a RWH-lease in step 2, while Samba only grants a
R-lease. Go figure...

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Sun May 28 18:52:52 CEST 2017 on sn-devel-144