staging: lustre: llite: a few fixes about readdir of striped dir.

Normally we know the value of op_mea1 when ll_readdir is called.
In the case of '.' or '..' op_mea1 is unknown so for that case
fetch the real parents FID.

Signed-off-by: wang di <di.wang@intel.com>
Signed-off-by: Li Xi <lixi@ddn.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4603
Reviewed-on: http://review.whamcloud.com/9191


Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Li Xi <pkuelelixi@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>