LU-16796 mgc: Change config_llog_data to use refcount_t

LU-16796 mgc: Change config_llog_data to use refcount_t

This patch changes struct config_llog_data to use refcount_t
instead of atomic_t

Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Ieec4de5d957b8dfa82c8cdef80f3a9f73aa55126
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52813
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>