EX-9449 csdc: replace assert with error message

EX-9449 csdc: replace assert with error message

Remove assert, based on the data from the wire and replace
it to the error message, which be useful in case this
error happens.

The -EAGAIN error is reasonable in this case.

Signed-off-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Change-Id: I2f37d0204123af1c23352b967dad1de5e7860b64
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54817
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>