[CI] Rerun flaky tests

[CagriYonca]

I'm taking the initiative and proposing the pytest-rerunfailures package for flaky tests. Only thing we should do is to add the line just before flaky tests:

    @pytest.mark.flaky(reruns=3, reruns_delay=2)   <-- ONLY THIS
    def test_flaky_test(self):
        ...