Fix XUnit parser softfail scenario

[pdostal]

The test case result was not properly set. This fixes it.

• Related ticket: poo#177321
• Related pull request: BCI: Softfail when BCI softfails os-autoinst-distri-opensuse#21304
• Previous pull request: Add softfail to XUnit parser #6227

[Martchus]

Avoid the repeated calls to $out->tag.

Maybe you can also add better tests this time.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.01%. Comparing base (a5ee6da) to head (06d1f7a).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6264   +/-   ##
=======================================
  Coverage   99.01%   99.01%           
=======================================
  Files         398      398           
  Lines       40017    40019    +2     
=======================================
+ Hits        39623    39625    +2     
  Misses        394      394           

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