fix: OnError call twice in svrTransHandler.OnRead

[Zzhiter]

What type of PR is this?

fix: svrTransHandler.OnError will be called twice when some error occured in svrTransHandler.OnRead
related issue：#1267

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修复 OnError 在 svrTransHandler.OnRead 中调用两次

(Optional) More detailed description for this PR(en: English/zh: Chinese).

什么原因造成的

在这个已经合入的PR中，#814
err由nil变为传递给外层

err被传递给外层，但是实际上外层的server是默认会对err进行处理的：

因此，err被处理了两次

解决办法

内层不再处理err，传递给外层的server处理

(Optional) Which issue(s) this PR fixes:

#1267

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.60%. Comparing base (d36f79e) to head (4e22bf4).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1272      +/-   ##
===========================================
+ Coverage    68.48%   68.60%   +0.12%     
===========================================
  Files          285      285              
  Lines        20646    20643       -3     
===========================================
+ Hits         14140    14163      +23     
+ Misses        5323     5305      -18     
+ Partials      1183     1175       -8     

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