EX-8362 scripts: Improve estimated ratio

EX-8362 scripts: Improve estimated ratio

ll_compression_scan does not take in account the size of the
sampled files, this might lead to uncorrect estimated ratio for non
homogeneous file.

This patch apply the compression ratio estimated with the sampled data
and applies it to the entire file size, assuming the file will have
the same compression ratio across it.

Test-Parameters: trivial
Signed-off-by: Raphael Druon <rdruon@ddn.com>
Change-Id: Ic4a26460e17c666b9edf4c0d8d450a06fad5920f
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52759
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>