in the StandardControllerServiceProvider, we enable a Collection of Controller Services but do so in the background with a limited number of threads. We need to ensure that all Controller Services have at least become ENABLING before returning from this method. Otherwise, Processors that depend on them could attempt to start. If this happens, the Processor will be invalid because it references a Disabled Controller Service. As a result, the Processor will not start. In a clustered environment, we will end up with inconsistent run states across the nodes.