s3/smbd: fix exclusive lease optimisation

s3/smbd: fix exclusive lease optimisation

We need to expect any amount of "stat" opens on the file without
triggering an assert.

This is the correct fix for bug #11844. I guess we haven't seens this
very often before bug #12766 got fixed, because most clients were using
LEASES instead of OPLOCKS.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12798

See also:
BUG: https://bugzilla.samba.org/show_bug.cgi?id=11844
BUG: https://bugzilla.samba.org/show_bug.cgi?id=12766

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>