coreutils, services: Refactor Open related logic

[Xuanwo]

Signed-off-by: Xuanwo github@xuanwo.io

[codecov]

Codecov Report

Merging #264 into master will decrease coverage by 0.11%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master     #264      +/-   ##
==========================================
- Coverage   84.18%   84.07%   -0.12%     
==========================================
  Files          12       12              
  Lines         936      948      +12     
==========================================
+ Hits          788      797       +9     
- Misses         92       94       +2     
- Partials       56       57       +1     

Impacted Files	Coverage Δ
services/fs/utils.go	80.64% <71.42%> (+1.33%)	⬆️
services/qingstor/utils.go	83.13% <72.00%> (-1.16%)	⬇️
services/qingstor/storager.go	76.78% <93.33%> (ø)
services/fs/storager.go	87.43% <100.00%> (ø)
services/qingstor/servicer.go	77.86% <100.00%> (-0.50%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7682686...df7f3de. Read the comment docs.