LUDOC-448 config: improve limits description

LUDOC-448 config: improve limits description

Improve the description of number of objects per OST to reflect that
this increases with the number of MDTs in the filesystem.  Also
increase the maximum ldiskfs and ZFS filesystem sizes used today.

Increase RAM sizes for MDS and OSS nodes to reflect current usage.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Icbacfc42ca0faa0e5aeba8372f09ca48413ebbe5
Reviewed-on: https://review.whamcloud.com/35334
Reviewed-by: Joseph Gmitter <jgmitter@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>