Fallback validation shouldn't allow to define fallback method on a subclass

[manovotn]

As was pointed out to me here, spec forbids to declare fallback methods on subclasses:

When fallbackMethod is used a FaultToleranceDefinitionException will be thrown if any of the following constraints are not met:

    The named fallback method must be on the same class, a superclass or an implemented interface of the class which declares the annotated method
    [...]
    The named fallback method must be accessible from the class which declares the annotated method

Currently, smallrye doesn't seem to check that and we just happen to pass the TCK because we actually blow up (with exactly the same exception) on validating the superclass alone.

[kenfinnigan]

Ouch, definitely need to fix that

[manovotn]

Yep, I'll send a PR for that once I am done with one another thing