We must release a port number after the shutdown and cleanup operation not before.It is a part of work forpostgrespro#249

This private method releases all the allocated node resources (port and so on).PostgresNode::__exit__ calls this new method instead free_port.

…is addedWhen this argument is True, cleanup calls _release_resources method.Default value is False.

…ed port number during failureNodeBackup::spawn_replica uses an explict "rollback" code to destroy a newly allocated node to release a reserved port number.