优化label筛选，没有选中label时不加载全部target

[xyctruth]

No description provided.

[codecov]

Codecov Report

Merging #33 (0735e85) into master (b679236) will increase coverage by 0.27%.
The diff coverage is 16.66%.

@@            Coverage Diff             @@
##           master      #33      +/-   ##
==========================================
+ Coverage   75.86%   76.14%   +0.27%     
==========================================
  Files          16       16              
  Lines         978      964      -14     
==========================================
- Hits          742      734       -8     
+ Misses        185      180       -5     
+ Partials       51       50       -1     

Flag	Coverage Δ
unittests	76.14% <16.66%> (+0.27%)	⬆️

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

Impacted Files	Coverage Δ
pkg/apiserver/api.go	71.34% <0.00%> (+2.41%)	⬆️
pkg/storage/store.go	40.00% <ø> (ø)
pkg/storage/badger/store.go	73.10% <28.57%> (-0.88%)	⬇️

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