Should not fail on abstract Collections for properties when using delegating Creator

[cowtowncoder]

(note: follow-up for #2251)

So, it looks like something like this:

    static class DelegatingWithAbstractSetter
    {
        Map<String, Object> _stuff;

        @JsonCreator(mode = JsonCreator.Mode.DELEGATING)
        public DelegatingWithAbstractSetter(Map<String, Object> stuff) {
            _stuff = stuff;
        }

        public void setNeverUsed(MyAbstractList bogus) { }
    }

fails with exception complaining that no deserializer can be found for abstract class MyAbstractList. Interestingly enough this is NOT problematic for simple abstract types (for which such code will not fail -- it either only fails for actual attempt at use, or something else is going on).
But since no setter or field would ever be used when there is a delegating creator, this is bogus problem, and should not cause failure.

Ideally Jackson would not even attempt resolution of setters when there is delegating creator.

[cowtowncoder]

No plans to try to fix this: users should @JsonIgnore such properties.