LU-9007 lod: improve obj alloc for FLR file

* add lod_layout_component::llc_ost_indices to track the map
  of dt_object to its OST index.
* add lod_device::lod_avoid to collect information of objects on other
  mirrors which overlapped the target component
* lod_should_avoid_ost() use the avoid guidance information to avoid
  allocating objects on the same OST for different mirrors.

Change-Id: Ib7e155e4b02c2e25d3955aa9a4acff7569ab7d8f
Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/32404
Reviewed-by: Jinshan Xiong <jinshan.xiong@gmail.com>
Reviewed-by: Patrick Farrell <paf@cray.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>