修复injector挂载sermant会跟skywalking产生冲突的问题

[provenceee]

【修复issue】 #1258

【修改内容】修改injector注入命令的行为

【用例描述】注入行为分别为before、after、ignore时，是否可以按预期注入命令

【自测情况】before时，在原命令前注入，after时，在原命令后注入，ignore时，不注入

【影响范围】需要更新文档

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: -0.02% ⚠️

Comparison is base (c5886c4) 45.55% compared to head (2556a16) 45.53%.
Report is 2 commits behind head on 1.0.x.

Additional details and impacted files

@@             Coverage Diff              @@
##              1.0.x    #1260      +/-   ##
============================================
- Coverage     45.55%   45.53%   -0.02%     
+ Complexity     2923     2921       -2     
============================================
  Files           676      676              
  Lines         14951    14946       -5     
  Branches       1679     1678       -1     
============================================
- Hits           6811     6806       -5     
  Misses         7296     7296              
  Partials        844      844              

Flag	Coverage Δ
unittests	45.53% <ø> (-0.02%)	⬇️

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see 1 file with indirect coverage changes

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