cluster: avoid redirect when grafana set root_url

[nexustar]

What problem does this PR solve?

• close tiup display show grafana is down when config root_url for grafana #2072

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release notes:

NONE

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AstroProfundis

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[codecov-commenter]

Codecov Report

Base: 55.19% // Head: 54.53% // Decreases project coverage by -0.66% ⚠️

Coverage data is based on head (fc858ff) compared to base (5c4bd1f).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2082      +/-   ##
==========================================
- Coverage   55.19%   54.53%   -0.66%     
==========================================
  Files         313      313              
  Lines       33173    33173              
==========================================
- Hits        18308    18089     -219     
- Misses      12672    12903     +231     
+ Partials     2193     2181      -12     

Flag	Coverage Δ
cluster	42.32% <100.00%> (-2.39%)	⬇️
dm	26.30% <100.00%> (+6.41%)	⬆️
playground	15.23% <0.00%> (ø)
tiup	16.47% <0.00%> (ø)
unittest	22.79% <0.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
pkg/cluster/spec/grafana.go	63.98% <100.00%> (-0.95%)	⬇️
pkg/cluster/api/cdcapi.go	0.00% <0.00%> (-53.49%)	⬇️
pkg/cluster/api/binlog.go	5.76% <0.00%> (-32.46%)	⬇️
pkg/cluster/operation/scale_in.go	23.51% <0.00%> (-25.39%)	⬇️
pkg/cluster/template/scripts/pd.go	15.79% <0.00%> (-21.05%)	⬇️
pkg/cluster/task/update_meta.go	63.48% <0.00%> (-19.13%)	⬇️
pkg/cluster/spec/cdc.go	40.22% <0.00%> (-19.02%)	⬇️
pkg/utils/retry.go	46.43% <0.00%> (-16.07%)	⬇️
pkg/cluster/manager/destroy.go	35.77% <0.00%> (-15.45%)	⬇️
pkg/cluster/spec/pd.go	54.68% <0.00%> (-13.11%)	⬇️
... and 34 more

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[nexustar]

/merge

[ti-chi-bot]

@nexustar: /merge in this pull request requires 1 approval(s).

In response to this:

/merge

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[nexustar]

/merge

[ti-chi-bot]

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

Commit hash: fc858ff