更新 engine CondDeleted 函数的实现

[ghost]

避免 在使用 postgres 数据库同时, 开启 deleted Tag 情况下
engine.Find 函数调用报错 pq: invalid input syntax for integer: "0001-01-01 00:00:00"

[codecov-io]

Codecov Report

Merging #1229 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1229      +/-   ##
==========================================
+ Coverage   57.35%   57.37%   +0.02%     
==========================================
  Files          43       43              
  Lines        7797     7801       +4     
==========================================
+ Hits         4472     4476       +4     
  Misses       2771     2771              
  Partials      554      554

Impacted Files	Coverage Δ
engine.go	61.7% <100%> (+0.17%)	⬆️

---

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 e410f04...856c971. Read the comment docs.

[lunny]

Could you add some tests?