Suicide trigger prevents cycles starting

[wxtim]

Description

User reported this case. It's not a blocker (for that user), because the user was over-using suicide triggers and we were able to remove the offending graph section. Nonetheless, this is a bug.

Reproducible Example

The following workflow will shut down as completed after all 1990's tasks are complete:

[scheduler]
    allow implicit tasks = True
    cycle point format = %Y

[scheduling]
    initial cycle point = 1990
    final cycle point = 1992
    [[graph]]
        R1 = install_cold
        P1Y = """
            install_cold[^] => foo? => bar?

            # The line below stops cycle points 1991 and 1992
            # from starting:
            bar:fail? => !foo?
        """

Expected Behaviour

Behaviour should be unchanged with or without the second graph line (assuming bar succeeds): 1991/2 should run the same graph again.

[wxtim]

The output of cylc graph looks correct.

[wxtim]

Conceivably the same issue as #5945 and #5730