ProtocolEventDebouncer calls refresh keyspace for the same keyspace multiple times

When a keyspace refresh event is present, the remaining handlers for that keyspace should be skipped just like when a global refresh event is present, every keyspace event is skipped.

https://github.com/datastax/csharp-driver/blob/e50547f6f57eec71dd309988b3e2ec5607be61c7/src/Cassandra/ProtocolEvents/ProtocolEventDebouncer.cs#L236-L253