NFSD or other lockmanager may increase the owner's reference,
so adds two new options for copying and releasing owner.

v5: change order from 2/6 to 3/6
v4: rename lm_copy_owner/lm_release_owner to lm_get_owner/lm_put_owner
Reviewed-by: NJeff Layton <jlayton@primarydata.com>
Signed-off-by: NKinglong Mee <kinglongmee@gmail.com>
Signed-off-by: NJeff Layton <jlayton@primarydata.com>