[ISSUE #774] Avoid cancel context too early cause trace data fail.

[lifepuzzlefun]

What is the purpose of the change

fix #774

current trace data can't send success.

Brief changelog

only cancel context when receive error or request finished.

Verifying this change

with this patch trace data can send succes.

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[lifepuzzlefun]

@duhenglucky @ShannonDing @yuz10 @maixiaohai can you take a look？thanks : - )

[guyinyou]

lgtm