Use UTC in es-index-cleaner

[pavolloffay]

Resolves #3228

[pavolloffay]

Do not merge yet!

[codecov]

Codecov Report

Merging #3261 (2fadf49) into master (ef8a559) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3261      +/-   ##
==========================================
- Coverage   95.85%   95.84%   -0.02%     
==========================================
  Files         259      259              
  Lines       15398    15398              
==========================================
- Hits        14760    14758       -2     
- Misses        549      552       +3     
+ Partials       89       88       -1     

Impacted Files	Coverage Δ
cmd/collector/app/server/zipkin.go	58.53% <0.00%> (-12.20%)	⬇️
pkg/config/tlscfg/cert_watcher.go	92.63% <0.00%> (-2.11%)	⬇️
plugin/storage/badger/spanstore/reader.go	96.21% <0.00%> (+0.70%)	⬆️
cmd/query/app/static_handler.go	98.80% <0.00%> (+1.19%)	⬆️

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