[HOTFIX] ModelCheckpoint - Don't increase current_epoch and global_step if not trained

[tchaton]

What does this PR do?

This PR resolve the bug associated with increasing current_epoch and global_step when iteratively dumping / restoring train.

Fixes #4176

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[pep8speaks]

Hello @tchaton! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2020-10-23 08:26:50 UTC

[codecov]

Codecov Report

Merging #4291 into master will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #4291   +/-   ##
======================================
  Coverage      93%     93%           
======================================
  Files         111     111           
  Lines        8007    8017   +10     
======================================
+ Hits         7445    7456   +11     
+ Misses        562     561    -1     

[mergify]

This pull request is now in conflict... :(