LU-16796 nodemap: Change nm_refcount to refcount

LU-16796 nodemap: Change nm_refcount to refcount

This patch changes struct lu_nodemap to use refcount_t instead
of atomic_t. Using refcount adds new functionally that we can
use with rhashtable which will be done in an follow on patch
for nodemaps.

Test-Parameters: trivial testlist=sanity-sec
Change-Id: I2651c24740ea43486398a200b76cf9eb29cdcdf7
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58453
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Marc Vef <mvef@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>