dr-autosync: do not switch to async when there is not enough peers

[disksing]

Signed-off-by: disksing i@disksing.com

What problem does this PR solve?

Issue Number: Close #4737

What is changed and how it works?

• In sync_recover state, if there is not majority peers, don't switch state.
• update test to make it more easy to read

Check List

Tests

• Unit test

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lhy1024
• nolouch

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[codecov]

Codecov Report

Merging #4738 (13749f4) into master (844d138) will decrease coverage by 0.05%.
The diff coverage is 65.13%.

@@            Coverage Diff             @@
##           master    #4738      +/-   ##
==========================================
- Coverage   75.14%   75.08%   -0.06%     
==========================================
  Files         284      287       +3     
  Lines       28038    28140     +102     
==========================================
+ Hits        21068    21129      +61     
- Misses       5107     5142      +35     
- Partials     1863     1869       +6     

Flag	Coverage Δ
unittests	75.08% <65.13%> (-0.06%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/storage/storage.go	64.86% <ø> (-5.41%)	⬇️
server/grpc_service.go	52.09% <45.45%> (-0.52%)	⬇️
tools/pd-ctl/pdctl/command/min_resolved_ts.go	50.00% <50.00%> (ø)
server/storage/endpoint/min_resolved_ts.go	55.55% <55.55%> (ø)
server/cluster/cluster.go	83.65% <61.11%> (-1.27%)	⬇️
server/api/min_resolved_ts.go	72.72% <72.72%> (ø)
server/api/router.go	99.58% <100.00%> (+<0.01%)	⬆️
server/config/config.go	77.94% <100.00%> (+0.09%)	⬆️
server/config/persist_options.go	93.63% <100.00%> (+1.90%)	⬆️
server/core/store.go	81.68% <100.00%> (+0.34%)	⬆️
... and 26 more

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[lhy1024]

/merge

[ti-chi-bot]

@lhy1024: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 5d8aadb