Maskrcnn num_image_candidates compliance

[nv-rborkar]

training rule described in https://github.com/mlcommons/training_policies/blob/master/training_rules.adoc#91-hyperparameters require num_image_candidates to be (1000 or 2000) or (1000 * batches per chip).

Current check only looks for multiple of 1000: https://github.com/mlcommons/logging/blob/master/mlperf_logging/compliance_checker/training_2.0.0/closed_maskrcnn.yaml#L64