bugfix:SetSlowThreshold not effective in function logDetails

[wwwangxc]

The slowThreshold is not used in the logDetails function to judge slow logs, so SetSlowThreshold not effective in function logDetails

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.54%. Comparing base (8690859) to head (854ee80).
Report is 186 commits behind head on master.

Additional details and impacted files

Files with missing lines	Coverage Δ
rest/handler/loghandler.go	100.00% <100.00%> (ø)

... and 5 files with indirect coverage changes