Update system/xattrs_linux.go

- Add Llistxattr() support
- Additionally cleanup Lgetxattr() and implement it properly
  in accordance with getxattr() syscall behavior.

Signed-off-by: Harshavardhana <fharshav@redhat.com>
xattr/xattr.go: Add new higher level helpers for xattr

Signed-off-by: Harshavardhana <fharshav@redhat.com>
Merge pull request #202 from harshavardhana/xattr_list_xattr

Update system/xattrs_linux.go