vfs_gpfs: Block punchhole calls for non-sparse files

vfs_gpfs: Block punchhole calls for non-sparse files

The core smbd code implements ZERO_DATA for non-sparse files by punching
a hole and filling it again with a fallocate(FL_KEEP_SIZE) call. As GPFS
does not provide the fallocate(FL_KEEP_SIZE) call and non-sparse files
should not contain holes, block the punchhole; effectively only allowing
ZERO_DATA/punchhole calls for sparse files.

Signed-off-by: Christof Schmitt <cs@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Tue Apr 23 00:33:03 UTC 2019 on sn-devel-144