Adjusted plugin registration way

[bsekachev]

Motivation and context

Previous one can lead to race condition, because plugin is listening for getting jobs requests.
If the weights loaded later than request occurs, it does not have opened job in memory and raises an error.
Rare but possible case.

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into the CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (see GitHub docs)
• I have increased versions of npm packages if it is necessary
  (cvat-canvas,
  cvat-core,
  cvat-data and
  cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[codecov]

Codecov Report

Merging #6533 (469d851) into develop (1da005c) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #6533      +/-   ##
===========================================
- Coverage    81.72%   81.72%   -0.01%     
===========================================
  Files          337      337              
  Lines        38516    38516              
  Branches      3547     3547              
===========================================
- Hits         31478    31476       -2     
- Misses        7038     7040       +2     

Components	Coverage Δ
cvat-ui	75.15% <100.00%> (ø)
cvat-server	87.80% <ø> (-0.02%)	⬇️