LU-18557 ldlm: save ldlm namespace ops for use

LU-18557 ldlm: save ldlm namespace ops for use

save ldlm namespace ops for use as __ldlm_resource_putref_final() can
initiate namespace release in a separate thread which in turn will
invalidate the structure pointing to the namespace's ops.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: If3ddc032b21806046fede09d40a4df78d441138d
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57432
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexey Lyashkov <alexey.lyashkov@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Mikhail Pershin <mpershin@whamcloud.com>