Fix ti-spark scale-out

[lucklove]

What problem does this PR solve?

Fix https://asktug.com/t/topic/37633

What is changed and how it works?

Just return emtpy version in version mapper and in download and deploy stage, we use the latest stable one if the version is empty.

Related changes

• Need to cherry-pick to the release branch

Release notes:

NONE

[codecov-io]

Codecov Report

Merging #901 (aa345a1) into master (cad0c4e) will decrease coverage by 0.01%.
The diff coverage is 22.22%.

@@            Coverage Diff             @@
##           master     #901      +/-   ##
==========================================
- Coverage   53.47%   53.46%   -0.02%     
==========================================
  Files         263      263              
  Lines       19067    19072       +5     
==========================================
  Hits        10197    10197              
- Misses       7294     7298       +4     
- Partials     1576     1577       +1     

Flag	Coverage Δ
cluster	45.45% <28.57%> (-0.01%)	⬇️
dm	25.25% <0.00%> (-0.07%)	⬇️
integrate	48.30% <22.22%> (-0.02%)	⬇️
playground	22.26% <0.00%> (-0.02%)	⬇️
tiup	10.84% <0.00%> (-0.01%)	⬇️
unittest	21.10% <0.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
cmd/mirror.go	36.85% <0.00%> (ø)
pkg/cluster/manager.go	67.95% <ø> (+0.09%)	⬆️
pkg/repository/v1_repository.go	64.73% <0.00%> (-0.83%)	⬇️
pkg/cluster/spec/bindversion.go	84.21% <100.00%> (+1.85%)	⬆️
pkg/cluster/api/dmapi.go	58.26% <0.00%> (-1.74%)	⬇️
pkg/cluster/api/pdapi.go	59.44% <0.00%> (-0.62%)	⬇️
pkg/utils/http_client.go	72.22% <0.00%> (+5.55%)	⬆️

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