LU-17013 lov: fill FIEMAP_EXTENT_LAST flag

LU-17013 lov: fill FIEMAP_EXTENT_LAST flag

If file has N extents and get the fiemap with exactly N
extent slots, the last extent will miss FIEMAP_EXTENT_LAST
flag. Fix it.

Lustre-change: https://review.whamcloud.com/51863
Lustre-commit: TBD (from 264ab0c258adbce93d582e5e97f05ff7bf87c18a)

Signed-off-by: Lei Feng <flei@whamcloud.com>
Test-Parameters: trivial testlist=sanityn env=ONLY="71a 71b 71c"
Change-Id: I4556b31f0d04bdf8e83f323e83b871b093beaa5e
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52114
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>