Refine pooled EntryOptions management

[luckyxiaoqiang]

Describe what this PR does / why we need it

Refine pooled EntryOptions management by putting it to pool at where we get it. Otherwise, it would be difficult to track its life cycle and not benefit to future maintenance.

Does this pull request fix one issue?

Describe how you did it

Describe how to verify it

Special notes for reviews

[codecov-io]

Codecov Report

Merging #277 into master will decrease coverage by 0.24%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #277      +/-   ##
==========================================
- Coverage   51.45%   51.20%   -0.25%     
==========================================
  Files          79       79              
  Lines        4033     4035       +2     
==========================================
- Hits         2075     2066       -9     
- Misses       1668     1679      +11     
  Partials      290      290              

Impacted Files	Coverage Δ
api/api.go	20.28% <0.00%> (-14.04%)	⬇️

---

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 908210d...0f02840. Read the comment docs.

[louyuting]

Thanks for contribution and look forward for more!