LU-16796 lnet: Change struct lnet_ping_buffer to use kref

LU-16796 lnet: Change struct lnet_ping_buffer to use kref

This patch changes struct lnet_ping_buffer to use
kref instead of atomic_t

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Ic180e576c3b11afec687dcb3b55b857c730598f6
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56177
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>