Disable openmp in static and dynamic histograms (#30072)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30072
Fix the test failure with mode/opt-lto by disabling openmp in both static and dynamic histograms. We will just use single thread in histogram processing as it's the common use case.
Test Plan:
```
buck run mode/opt caffe2/caffe2/fb/fbgemm/numerical_debugger/workflows:int8_static_quantization_exporter -- --model-dir /mnt/public/summerdeng/ads/ --model-name downsized_ins_97293388_0.predictor --run --iter 10 --dataset-path /mnt/public/summerdeng/ads/ctr_instagram_story_int8/dataset/train/dataset_115764229_10 --hive-path="hive://ad_delivery/ig_ad_prefiltered_training_data_orc_injected/ds=2019-09-09/pipeline=ctr_instagram_story_click_only_model_opt_out_df" --collect-histogram --activation-histogram-file=/mnt/public/summerdeng/ads/ctr_instagram_story_int8/activation_histograms/dummy_debug_OOM.txt
```
```
buck test mode/opt-lto caffe2/caffe2/quantization/server:dynamic_histogram_test -- --run-disabled
```
Reviewed By: hx89
Differential Revision: D18554614
fbshipit-source-id: cfff51174154e753b7123b4ec502b88ffc508917
