Refine the log errs in scheduler (#2705)

[ti-srebot]

cherry-pick #2705 to release-4.0

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Signed-off-by: lhy1024 admin@liudos.us

What problem does this PR solve?

To solve #2704

What is changed and how it works?

Check List

Tests

• Unit test

Release note

• No release note

[lhy1024]

/run-all-tests

[lhy1024]

/run-integration-ddl-test

[codecov]

Codecov Report

Merging #2900 into release-4.0 will decrease coverage by 0.03%.
The diff coverage is 25.00%.

@@               Coverage Diff               @@
##           release-4.0    #2900      +/-   ##
===============================================
- Coverage        77.41%   77.38%   -0.04%     
===============================================
  Files              210      210              
  Lines            22780    22784       +4     
===============================================
- Hits             17636    17631       -5     
- Misses            3813     3822       +9     
  Partials          1331     1331              

Impacted Files	Coverage Δ
server/cluster/cluster_worker.go	72.95% <0.00%> (ø)
server/schedulers/balance_region.go	85.38% <0.00%> (ø)
server/schedulers/base_scheduler.go	69.56% <0.00%> (ø)
server/schedulers/hot_region.go	82.11% <0.00%> (ø)
server/schedulers/label.go	74.24% <0.00%> (ø)
server/schedulers/random_merge.go	64.17% <0.00%> (ø)
server/schedulers/scatter_range.go	83.01% <0.00%> (ø)
server/schedulers/shuffle_hot_region.go	74.78% <0.00%> (ø)
server/schedulers/shuffle_region.go	83.52% <0.00%> (ø)
server/schedulers/utils.go	92.17% <0.00%> (ø)
... and 18 more

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[lhy1024]

/run-all-tests

[nolouch]

LGTM

[lhy1024]

@rleungx PTAL. Can we merge it?

[nolouch]

/merge

[ti-srebot]

/run-all-tests