Remove file system sharemode before calling unlink

Remove file system sharemode before calling unlink

GPFS implements the DENY_DELETE sharemode, which prevents unlink() from
deleting the file.. This causes the problem that deleting a file through
"delete on close" fails, as the code in close.c first calls unlink() and
only later removes the file system sharemode.

Fix this by removing the file system sharemode before calling unlink().

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13217

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Christof Schmitt <cs@samba.org>
Autobuild-Date(master): Wed Jan 17 01:31:53 CET 2018 on sn-devel-144