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.

Lustre-change: https://review.whamcloud.com/52128
Lustre-commit: 79f823bd40ee97a5846d828efce1080dc04a6057

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I53c5cb14f9a5630fc269d97cead9a5ca6a33895e
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Aurelien Degremont <adegremont@nvidia.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/52369
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>