LU-2569 test: use xattr.h from sys.

glibc now provides sys/xattrs.h. This is used over the
old attr/xattr.h originally provided by SGI.

Signed-off-by: Richard Henwood <richard.henwood@intel.com>
Change-Id: Ie3ca5b53e8a1a71ac2b51431780c5dbc19e18594
Reviewed-on: http://review.whamcloud.com/4946
Tested-by: Hudson
Reviewed-by: Christopher J. Morrone <chris.morrone.llnl@gmail.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>