Only use xUnit type JUnit for *.xunit.xml results if pytest compliant (#831)
Only use xUnit type JUnit for *.xunit.xml results if pytest compliant (#831)

Sometimes pytest results are put into files with extension *.xunit.xml,
for example, if added with `ament_cmake_pytest`.

Signed-off-by: Jacob Perron <f862f167b85d41b225785c70d70808bc7337c1fe@openrobotics.org>
ros-infrastructure/ros_buildfarm,ros-infrastructure/ros_buildfarm,ros-infrastructure/ros_buildfarm