[Fix] Fix meta information loading in runner.resume

[yeliudev]

The original runner.resume method loads all the meta information in the checkpoint, including epoch, iter, mmcv_version, mmdet_version (optional) into runner.meta. And these information will wrongly override the meta in subsequent checkpoints in runner.save_checkpoint. See here.

[codecov]

Codecov Report

Merging #1105 (d86525f) into master (004c006) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1105      +/-   ##
==========================================
- Coverage   67.62%   67.62%   -0.01%     
==========================================
  Files         159      159              
  Lines       10283    10282       -1     
  Branches     1857     1857              
==========================================
- Hits         6954     6953       -1     
  Misses       2964     2964              
  Partials      365      365              

Flag	Coverage Δ
unittests	67.62% <ø> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
mmcv/runner/base_runner.py	77.38% <ø> (-0.09%)	⬇️

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[yeliudev]

Duplicate #1108.

[ZwwWayne]

Directly remove that might be inappropriate. We plan to merge #1108 to fix this issue, so this PR is closed.