LU-1445 osp: Use FID to track precreate cache.

LU-1445 osp: Use FID to track precreate cache.

Change last_used/pre_used/pre_created_id to real fid, so
to track precreate cache with real fid.

For simplicity, precreate/orphan_cleanup between osp and
OFD must be within the same sequence.

Precreate process will be:

1. OSP will request one sequence from OST initially.

2. During precreation, osp will allocate a group of fids
for the precreation request within the current sequence,
then send the request to OST(OFD) with these fids.

3. When getting the precreate request, OST will precreate
the objects by those fids in the request.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: Ib7f1016321c064656158c54f4475922a199e19b3
Reviewed-on: http://review.whamcloud.com/4789
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>