backend: DRY on check_socket method

[okurz]

No description provided.

[codecov]

Codecov Report

Merging #1185 into master will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1185      +/-   ##
==========================================
- Coverage   40.01%   39.99%   -0.03%     
==========================================
  Files          40       40              
  Lines        4868     4868              
  Branches      828      828              
==========================================
- Hits         1948     1947       -1     
  Misses       2588     2588              
- Partials      332      333       +1

Impacted Files	Coverage Δ
backend/qemu.pm	32.46% <0%> (-0.19%)	⬇️

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