Potential deadlock when triggering a blocking snapshot in case of non-source signals

This change https://github.com/debezium/debezium/pull/5227 moved registration of signal actions just before the start of the streaming to permit to correctly trigger an incremental snapshot when using a non-source channel. 

Now a blocking snapshot signal is processed but it will assume that the streaming is running and ChangeEventSourceCoordinator waits until the streaming will be paused, but can happen that the streaming is not started yet.