vfs_gpfs: Retry getacl with DAC capability if necessary

vfs_gpfs: Retry getacl with DAC capability if necessary

Samba always tries to read the ACL of a file and checks it internally.
If the READ_ACL permission is missing in GPFS, then then reading the ACL
for Samba internal evaluation will be denied and opening the file or
directory fails. Change this by retrying reading the ACL with the DAC
capability if access was denied.

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): Mon Jul 25 10:30:02 CEST 2016 on sn-devel-144