vfs_gpfs: use handle based gpfswrap_get_winattrs()

vfs_gpfs: use handle based gpfswrap_get_winattrs()

Fixes detecting offline flag for files in snapshot – no idea if this is
actually expected.

Replaces path based gpfswrap_get_winattrs_path() with handle based version
gpfswrap_get_winattrs(). When dealing with files in snapshots fsp->fsp_name
points to the active dataset, which will cause ENOENT failures if files are
deleted there any only present in the snapshot.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15069

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Christof Schmitt <cs@samba.org>