LU-9750 nrs: some code cleanup in NRS policies

LU-9750 nrs: some code cleanup in NRS policies

This patch does some code cleanup in NRS CRR and ORR polices,
including:
- remove the useless NULL checks
- handle errors properly by multiple labels instead of a single one

Lustre-change: https://review.whamcloud.com/25319
Lustre-commit: 647d9d34be28e53d72606030461d8516979e8590

Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Change-Id: Iafe86ac94042547e83c69e4b46ff7bf1ca31f073
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/28231
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>