ipatests: Specify Pytest XML report schema
    
    Pytest 5.2+ warns if tests XML report is generated but its format (schema)
    is not explicitly specified:
    ```
    /root/.local/lib/python3/site-packages/_pytest/junitxml.py:417
      /root/.local/lib/python3/site-packages/_pytest/junitxml.py:417: PytestDeprecationWarning: The 'junit_family' default value will change to 'xunit2' in pytest 6.0.
      Add 'junit_family=xunit1' to your pytest.ini file to keep the current format in future versions of pytest and silence this warning.
        _issue_warning_captured(deprecated.JUNIT_XML_DEFAULT_FAMILY, config.hook, 2)
    ```
    
    For example, xunit2 is used by jenkins and Pytest strictly conforms its
    schema [0]. Pytest's xunit1, in turn, allows to attach user fields to
    report.
    
    The only known client of IPA tests results is Azure. Azure supports
    [1] JUnit, which is likely the same as Pytest's xunit1, while Azure's
    xUnit2 is actually xUnit.net v2. This means that Azure supports (in
    one form or another) Pytest's both xunit1 and xunit2 as JUnit.
    
    [0]: https://github.com/jenkinsci/xunit-plugin/blob/xunit-2.3.2/src/main/resources/org/jenkinsci/plugins/xunit/types/model/xsd/junit-10.xsd
    [1]: https://docs.microsoft.com/en-us/azure/devops/pipelines/tasks/test/publish-test-results?view=azure-devops&tabs=yaml
    
    Fixes: https://pagure.io/freeipa/issue/8101
    Signed-off-by: Stanislav Levin <slev@altlinux.org>
    Reviewed-By: Sergey Orlov <sorlov@redhat.com>