[Fix] Bugs in nms

[filaPro]

Motivation

Fix bugs introduced in #1403. This is also related to mmcv#1902.

Modification

Fix bugs, add tests from mmcv.

[codecov]

Codecov Report

Merging #1479 (e895dd1) into dev (4422eaa) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##              dev    #1479      +/-   ##
==========================================
- Coverage   50.39%   50.38%   -0.01%     
==========================================
  Files         221      221              
  Lines       18927    18928       +1     
  Branches     3118     3118              
==========================================
- Hits         9538     9537       -1     
- Misses       8811     8814       +3     
+ Partials      578      577       -1     

Flag	Coverage Δ
unittests	50.38% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
mmdet3d/core/post_processing/box3d_nms.py	27.89% <0.00%> (-0.88%)	⬇️
mmdet3d/datasets/pipelines/test_time_aug.py	51.04% <0.00%> (ø)

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[filaPro]

Also put bboxes, labels and scores in the test_merge_aug_bboxes_3d to the same device. scores are updated for more determinism in case of equal values.