LU-17015 obdclass: make upcall cache hashtable size dynamic

LU-17015 obdclass: make upcall cache hashtable size dynamic

The hash table used by the upcall cache mechanism should have an
adjustable size, depending on the purpose and context where it is
used.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I53c5cb14f9a5630fc269d97cead9a5ca6a33895e
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52128
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Aurelien Degremont <adegremont@nvidia.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>