EX-4015 lipe: cache layout in loa

EX-4015 lipe: cache layout in loa

In ldiskfs_read_attr_lov(), cache the decoded llapi_layout() in the
current object attrs. Then resue this layout in lov-pools. Add
lov-ost-indexes to return a list of all object OST indexes for the
current file.

Test-Parameters: trivial testlist=sanity-lipe-scan3 facet=mds1
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I3451857fc25f1f9507b6e185bad39fcb3f0e6f22
Reviewed-on: https://review.whamcloud.com/46546
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>