Do not override the logged epoch in logged_metrics

[carmocca]

What does this PR do?

• Do not override the logged epoch if available.
• Early return in log_metrics

Fixes #7882 (comment)

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[codecov]

Codecov Report

Merging #7982 (37531d4) into master (d2983c7) will decrease coverage by 0%.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master   #7982    +/-   ##
=======================================
- Coverage      92%     91%    -0%     
=======================================
  Files         207     207            
  Lines       13380   13503   +123     
=======================================
+ Hits        12252   12330    +78     
- Misses       1128    1173    +45     

[tchaton]

LGTM !