LU-14155 mdc: avoid easize set to 0

LU-14155 mdc: avoid easize set to 0

The cl_default_mds_easize could be set to 0 in some case. Then
check it before package.

Fixes: 3ec712bd183a ("LU-11868 osd: Set max ea size to XATTR_SIZE_MAX")
Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: Icc045bfba345a61dd7904bfc7772930fd737334e
Reviewed-on: https://review.whamcloud.com/40785
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>