staging: lustre: lmv: revalidate the dentry for striped dir

If there are bad stripe during striped dir revalidation,
most likely due the race between close(unlink) and
getattr, then let's revalidate the dentry, instead of
return error, like normal directory.

Signed-off-by: wang di <di.wang@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6831
Reviewed-on: http://review.whamcloud.com/15720
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-7078
Reviewed-on: http://review.whamcloud.com/16382


Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: John L. Hammond <john.hammond@intel.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>