LU-9840 lod: add ldo_dir_stripe_loaded

LU-9840 lod: add ldo_dir_stripe_loaded

Add ldo_dir_stripe_loaded flag to avoid loading
stripes mulitple times especcially for non-stripe
directory.

Lustre-change: https://review.whamcloud.com/28962
Lustre-commit: 744fe412fa101609a38f7ccc77efc4f1c540e008

Change-Id: Ia9360aac9e24706e401184c75fae4ec7f8ec46d9
Signed-off-by: Di Wang <di.wang@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-on: https://review.whamcloud.com/29143
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>