staging: lustre: mdt: add indexing option to default dir stripe

Add indexing option to default dirstripe EA. If MDT find
out the client send the create req to the wrong MDT because
of default stripeEA, it will return -EREMOTE, then client
will retrieve default stripeEA through xattr cache, and
re-create the object.

Also merged patch for LU-6341 to resolve the following problem.
Use ll_dir_getstripe to get default stripeEA in ll_new_node(),
Because ll_getxattr_common requires admin rights for retrieving
default LMVEA (because of trusted- prefix), which might cause
mkdir (from normal user) failure.

If parent does not have default stripeEA, then child should always
be in the same MDT for mkdir. Otherwise MDT should return -EREMOTE,
then client will refresh the default stripe index, and recreate
the object.

Signed-off-by: wang di <di.wang@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-5523
Reviewed-on: http://review.whamcloud.com/13360
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-6341
Reviewed-on: http://review.whamcloud.com/13990


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.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>