修复 is_ajax() 判断失效的问题

[hhyo]

fix #1884

[codecov]

Codecov Report

Base: 75.91% // Head: 75.95% // Increases project coverage by +0.03% 🎉

Coverage data is based on head (3740128) compared to base (cc70b96).
Patch coverage: 88.23% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1896      +/-   ##
==========================================
+ Coverage   75.91%   75.95%   +0.03%     
==========================================
  Files          91       91              
  Lines       14186    14195       +9     
==========================================
+ Hits        10770    10782      +12     
+ Misses       3416     3413       -3     

Impacted Files	Coverage Δ
common/utils/permission.py	48.27% <50.00%> (+11.23%)	⬆️
common/tests.py	100.00% <100.00%> (ø)
sql/views.py	63.45% <0.00%> (-0.67%)	⬇️
sql/engines/goinception.py	64.92% <0.00%> (-0.33%)	⬇️
sql/engines/mssql.py	70.05% <0.00%> (-0.16%)	⬇️
sql/engines/mongo.py	50.00% <0.00%> (+0.13%)	⬆️
sql/utils/sql_utils.py	63.51% <0.00%> (+0.42%)	⬆️

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