LU-541 Fix getstripe interop with 2.0 server

LU-541 Fix getstripe interop with 2.0 server

* 2.0 server has changed dir getstripe rule as follows:
          If the directory in question DOES NOT have it's EA set, AND it
          IS NOT the root directory of the filesystem, then no EA values
          are returned to userspace. Rather, an error is returned from
          the ioctl and errno is set to ENODATA.
  1.8 client needs adapt to this rule
* fix liblustreapi.c usage of errno and rc, llapi_xxx() functions should
  return negative value on error.

Change-Id: If81a456209d5985aae7f20569eba1ac45ef576b1
Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1154
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>