UI Topology Visualization should not check sys streams by default

New system streams (beginning with two underscores __) have been added since the visualization code was added, such as __ack_reset_timeout and __eventlog. The visualization code currently presents stream check boxes as unchecked if they are ack-related streams and checked otherwise.

It seems that it should present only non-system streams as checked, so that the graph shows more relevant streams by default.