LU-18086 obdclass: change POOLS_COUNT

LU-18086 obdclass: change POOLS_COUNT

POOLS_COUNT must guarantee that page_pools
largest pool size is 2 * MAX_BRW_SIZE.
Take into account that pool_order is a power
of 2 number of pages. Previous logic assumed
that pool_order is a power of 2 bytes. That
said, there were 27 pools to provide 64MB*2
pool(the largest pool). As maximum pool pages
is cfs_totalram_pages / POOLS_COUNT, it made
pools too small. For example, for system with
3G RAM pool with order 0(1 page) maximum pool
size would be about 100MB. It might cause
-ENOMEM despite the fact there is enough memory
in a system.

Also added, that every pool must have at
least one object.

Signed-off-by: Sergey Cheremencev <scherementsev@ddn.com>
Signed-off-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Change-Id: I872f4bdda392d7675b26b2f59ac2520208a96fa0
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55915
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>