[TIP] skipped testcases not reported in JUnit XML

[Pere Martir]

> When we last discussed this kohusuke felt it was a good backstop
> against broken configurations (no tests actually run is more likely to
> indicate a broken setup than a successful test run on a brand new
> project).

Good point. However, if each test case is executed in a separated
downstream job of a matrix job, the build result of the parent matrix
job will be considered "failed"  if any of the downstream job/test
case is skipped. This is actually what is happening to me.