When updating Parameter Context, some processors may fail to restart

When a Parameter Context is updated, it must stop any processors that will be affected by the update. The context is then updated, and any processor that was stopped is then restarted (assuming that it is still valid after the update).

In NIFI-7536 we improved the efficiency of waiting for processors to complete the action of stopping. However, it appears that in this fix, we caused a new problem. If a Processor that is affected by the Parameter Context is stopped, and then takes a long time to complete validation, that Processor may not be started again.

Note that this issue only affects the 'main' branch and hasn't yet been released.