Handle non-function scope for async fixtures

[altendky]

@pytest.mark.skip
def test_async_fixture_module_scope(testdir, cmd_opts):
    test_file = """
    from twisted.internet import reactor, defer
    import pytest
    import pytest_twisted

    check_me = 0

    @pytest_twisted.async_yield_fixture(scope="module")
    async def foo():
        global check_me

        if check_me != 0:
            raise Exception('check_me already modified before fixture run')

        check_me = 1

        yield 42

        if check_me != 3:
            raise Exception(
                'check_me not updated properly: {}'.format(check_me),
            )

        check_me = 0

    def test_first(foo):
        global check_me

        assert check_me == 1
        assert foo == 42

        check_me = 2

    def test_second(foo):
        global check_me

        assert check_me == 2
        assert foo == 42

        check_me = 3
    """
    testdir.makepyfile(test_file)
    rr = testdir.run(sys.executable, "-m", "pytest", "-v", *cmd_opts)
    assert_outcomes(rr, {"passed": 2})