scheduler: fix the issue that some scheduler persist config without solving error (#2817)

[ti-srebot]

cherry-pick #2817 to release-4.0

---

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

What problem does this PR solve?

fix the issue that some scheduler persist config without solving error

What is changed and how it works?

return with error

Check List

Tests

• Unit test

Release note

[rleungx]

LGTM

[nolouch]

LGTM

[codecov]

Codecov Report

Merging #2818 into release-4.0 will increase coverage by 0.31%.
The diff coverage is 100.00%.

@@               Coverage Diff               @@
##           release-4.0    #2818      +/-   ##
===============================================
+ Coverage        77.56%   77.87%   +0.31%     
===============================================
  Files              208      208              
  Lines            22768    22765       -3     
===============================================
+ Hits             17660    17729      +69     
+ Misses            3792     3708      -84     
- Partials          1316     1328      +12     

Impacted Files	Coverage Δ
server/schedulers/evict_leader.go	72.24% <100.00%> (-0.14%)	⬇️
server/schedulers/grant_leader.go	71.66% <100.00%> (-0.16%)	⬇️
server/schedulers/scatter_range.go	83.01% <100.00%> (-0.11%)	⬇️
pkg/etcdutil/etcdutil.go	86.95% <0.00%> (-4.35%)	⬇️
server/kv/etcd_kv.go	84.41% <0.00%> (-3.90%)	⬇️
server/tso/tso.go	82.27% <0.00%> (-3.80%)	⬇️
server/cluster/coordinator.go	70.74% <0.00%> (-1.20%)	⬇️
server/server.go	76.82% <0.00%> (-1.19%)	⬇️
pkg/btree/btree.go	86.84% <0.00%> (-0.81%)	⬇️
server/member/leader.go	74.70% <0.00%> (-0.78%)	⬇️
... and 7 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 57f6db1...9203749. Read the comment docs.

[lhy1024]

/merge

[ti-srebot]

Your auto merge job has been accepted, waiting for:

• 2871
• 2871

[lhy1024]

/merge

[ti-srebot]

Your auto merge job has been accepted, waiting for:

• 2871
• 2871

[ti-srebot]

/run-all-tests