scheduler: fix reservation reserved updated

[saintube]

Ⅰ. Describe what this PR does

koord-scheduler: fix a bug where the reserved in a Reservation does not refresh for the Update event.

Ⅱ. Does this pull request fix one issue?

related to #2315.

Ⅲ. Describe how to verify it

Ⅳ. Special notes for reviews

V. Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in make test

[ZiMengSheng]

/lgtm

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.98%. Comparing base (79036cf) to head (3b18165).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2322      +/-   ##
==========================================
- Coverage   66.09%   65.98%   -0.11%     
==========================================
  Files         458      458              
  Lines       54200    54205       +5     
==========================================
- Hits        35823    35769      -54     
- Misses      15803    15871      +68     
+ Partials     2574     2565       -9     

Flag	Coverage Δ
unittests	65.98% <100.00%> (-0.11%)	⬇️

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[zwzhang0107]

/approve