LU-17692 llite: flock work with lockd

LU-17692 llite: flock work with lockd

Change the flock to invoke lock copy API to work
with nfs server.

Fixes: 7f8af8f37e ("LU-17692 flock: get extra reference for lockd")
Signed-off-by: Yang Sheng <ys@whamcloud.com>
Change-Id: Ic5b3daf825dfa616a394c47a76f0d08e87c5bc9a
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56488
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Zhenyu Xu <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>