Infinite loop when processing recursive references

[niuhf0452]

Example:

    @JsonSubTypes({
            @JsonSubTypes.Type(value = AImpl.class)
    })
    abstract class A {
    }

    class AImpl extends A {
        public B b;
    }

    @JsonSubTypes({
            @JsonSubTypes.Type(value = BImpl.class)
    })
    abstract class B {
    }

    class BImpl extends B {
        public A a;
    }

When parsing these models with ApiModelParser, it falls into infinitely looping.