Address xfail unit test

[mfitz]

The unit test test_core_schedule_elements.py::test_splitting_service_edge_case_on_direction_results_in_two_directions is currently marked as xfail, meaning it is executed as normal with the test suite, but expected to fail (which it does). After removing the xfail decorator:

test_core_schedule_elements.py::test_splitting_service_edge_case_on_direction_results_in_two_directions FAILED [100%]
tests/test_core_schedule_elements.py:599 (test_splitting_service_edge_case_on_direction_results_in_two_directions)
[{'1_dir_1'}, {'2_dir_2'}, {'3_dir_1'}, {'4_dir_1'}] != [{'3_dir_1', '4_dir_1', '1_dir_1'}, {'2_dir_2'}]

Expected :[{'3_dir_1', '4_dir_1', '1_dir_1'}, {'2_dir_2'}]
Actual   :[{'1_dir_1'}, {'2_dir_2'}, {'3_dir_1'}, {'4_dir_1'}]
<Click to see difference>

service_edge_case_loopy_and_non_overlapping_graph = <Service instance at 5144736848: with 4 routes>

    def test_splitting_service_edge_case_on_direction_results_in_two_directions(
            service_edge_case_loopy_and_non_overlapping_graph):
        routes, graph_groups = service_edge_case_loopy_and_non_overlapping_graph.split_graph()
>       assert routes == [{'1_dir_1', '3_dir_1', '4_dir_1'}, {'2_dir_2'}]
E       AssertionError: assert [{'1_dir_1'}, {'2_dir_2'}, {'3_dir_1'}, {'4_dir_1'}] == [{'3_dir_1', '4_dir_1', '1_dir_1'}, {'2_dir_2'}]

test_core_schedule_elements.py:603: AssertionError

Assertion failed

We shouldn't leave the test as xfail, we should address why the test is failing, fix whatever needs fixing, and reintroduce the test to the test suite.