fix unit test unstable problem

[EvenLjj]

Sometimes localhost will resolve to an IPv6 address.

[codecov[bot]]

Codecov Report

Merging #1355 (c92ebc5) into master (3c750e4) will decrease coverage by 0.03%. The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1355      +/-   ##
============================================
- Coverage     72.10%   72.07%   -0.03%     
- Complexity      783      784       +1     
============================================
  Files           416      416              
  Lines         17661    17661              
  Branches       2752     2752              
============================================
- Hits          12735    12730       -5     
- Misses         3523     3525       +2     
- Partials       1403     1406       +3     

see 2 files with indirect coverage changes