cluster: fix tispark master scaling handling

[AstroProfundis]

What problem does this PR solve?

Make it possible for broken clusters to fix no tispark master error by scaling out a new tispark master node

What is changed and how it works?

Ignore topology validation error when listing clusters, this is a following up of #920

Check List

Tests

• Manual test (add detailed scripts or steps below)

Code changes

• Has exported function/method change

Related changes

• Need to cherry-pick to the release branch

Release notes:

NONE

[codecov-io]

Codecov Report

Merging #924 (d6eaae0) into master (5116917) will increase coverage by 0.03%.
The diff coverage is 45.00%.

@@            Coverage Diff             @@
##           master     #924      +/-   ##
==========================================
+ Coverage   53.11%   53.14%   +0.03%     
==========================================
  Files         260      260              
  Lines       18946    18956      +10     
==========================================
+ Hits        10063    10074      +11     
- Misses       7339     7340       +1     
+ Partials     1544     1542       -2     

Flag	Coverage Δ
cluster	45.18% <45.00%> (+0.03%)	⬆️
dm	25.05% <10.00%> (+0.02%)	⬆️
integrate	47.74% <45.00%> (+0.03%)	⬆️
playground	22.09% <ø> (ø)
tiup	10.67% <0.00%> (-0.01%)	⬇️
unittest	21.51% <10.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
pkg/cluster/spec/spec_manager.go	62.31% <12.50%> (+0.55%)	⬆️
pkg/cluster/manager.go	67.75% <50.00%> (+0.12%)	⬆️
pkg/cluster/operation/scale_in.go	59.87% <70.00%> (+0.68%)	⬆️
pkg/cluster/api/pdapi.go	59.44% <0.00%> (-0.62%)	⬇️
pkg/cluster/api/dmapi.go	60.00% <0.00%> (+1.73%)	⬆️
pkg/utils/http_client.go	72.22% <0.00%> (+5.55%)	⬆️

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[lucklove]

LGTM