Allow BeanManager methods, such as getBeans in AfterDeploymentValidation observers

CDI-274 which disallows some BeanManager methods during application initialization is too strict.

Mark's original suggestion for CDI-274 contained a very important part "...before the AfterDeploymentValidation phase". AfterDeploymentValidation observers would be quite useless if we can't use BeanManager.getBeans in them IMHO, and I think there is no reason to disallow BeanManager methods in AfterDeploymentValidation, so we should allow them there...

So maybe something like:
"IllegalStateException if called during application initialization before the AfterDeploymentValidation phase"