LU-1482 mdd: Setting xattr are properly checked with and without ACLs

LU-1482 mdd: Setting xattr are properly checked with and without ACLs

Setting extended attributes permissions are properly checked with and
without ACLs. In user.* namespace, only regular files and directories
can have extended attributes. For sticky directories, only the owner
and privileged user can write attributes.

Intel-bug-id: LDEV-40
Intel-change: http://review.whamcloud.com/15848

Change-Id: Ibd79dcc15e61839d878f4847f7836f29d823be61
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: http://review.whamcloud.com/21496
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>