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>
yep, a line should do. Just because this is a low level function and expects users to supply a buffer and returns size. IMO, we can have a helper that returns a friendly array but that could be another PR :)