Wrong check of assigned RabbitAdmin in getDeclaringAdmins() causing declarables to fail declaration or to be declared in the wrong broker

[rwanderc]

As per GH-18, the approach of injecting the RabbitAdmin into the setAdminsThatShouldDeclare() was changed to avoid premature initialization of the RabbitAdmin bean. The change was to inject the name of the bean instead of the real instance.
However, the check for the assignment of the RabbitAdmin was still looking for the bean and replacing the name of the bean with the latest name.
This led to failures to declare queues/exchanges/bindings or the declaration happens in the wrong broker.

Affected versions: 2.3.0, 2.2.2, 2.2.1, 2.1.5, 2.1.6