EX-7601 csdc: improve preview warning messages

EX-7601 csdc: improve preview warning messages

Avoid printing duplicate warning messages on the console when
creating files with multiple compressed components.  On the
flip side, log a console message when compression is enabled
so that this will later be visible if enabled on a system.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I8cb2f67689824513335f3fa65e9ea751923ebbe5
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53045
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Artem Blagodarenko <ablagodarenko@ddn.com>