EX-9784 csdc: Do not print error if a chunk is not compressed

EX-9784 csdc: Do not print error if a chunk is not compressed

is_chunk_start() can decide that a chunk can not be decompressed in
two cases: 1) chunk has not been compressed 2) chunk is corrupted

The error message should be printed only in case 2)

Signed-off-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Change-Id: I85f4850f989ba0fc8f00653f8f6b0f1b4837d625
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/55128
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sergey Cheremencev <scherementsev@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>