staging: lustre: llite: eat -EEXIST on setting trusted.lov

Tools like rsync, tar, cp may copy and restore the xattrs on a file.
The client previously ignored the setting of trusted.lov/lustre.lov
if the layout had already been specified, to avoid causing these
tools to fail for no reason.

For PFL files we still need to silently eat -EEXIST on setting these
attributes to avoid problems.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-9484
Reviewed-on: https://review.whamcloud.com/27126


Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>