fix test unit of nms and batched_nms for tensorrt

[RunningLeon]

This PR fix test units of nms and batched_nms in test_tensorrt.py.

[codecov]

Codecov Report

Merging #872 (98e84f4) into master (27e9ede) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #872   +/-   ##
=======================================
  Coverage   66.46%   66.46%           
=======================================
  Files         145      145           
  Lines        8781     8781           
  Branches     1599     1599           
=======================================
  Hits         5836     5836           
  Misses       2629     2629           
  Partials      316      316           

Flag	Coverage Δ
unittests	66.46% <ø> (ø)

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