NIFI-6807: When a Controller Service's state is transitioned to ENABL…

[markap14]

…ING, complete the Future successfully, even if the Controller Service is not valid. The Controller Service will remain in the ENABLING state until it is made valid, at which point it will ENABLE (unless explicitly disabled first). This allows us to Enable a Controller Service and its referencing components, even if the referencing component is still invalid due to it not yet recognizing the the referenced service has been enabled.

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Enables X functionality; fixes bug NIFI-YYYY.

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[mcgilman]

Will review...

[mcgilman]

Thanks @markap14! This has been merged to master.