EX-9196 csdc: do not round lnb size up to the PAGE_SIZE

EX-9196 csdc: do not round lnb size up to the PAGE_SIZE

lnb size is successfully updated to the right one in case the chunk
has been decompressed but left equual to the PAGE_SIZE in case it
hasn't. This leads to the wrong file size change.

This patch set lnb size before the decompression, so if lnb hasn't
decompressed this size is left as is.

Signed-off-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Test-Parameters: trivial testlist=sanity-compr env=ONLY=1003
Change-Id: I4b8149cc3aab1973a1a261b2e164c321019a437e
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54518
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>