bandwidth_views should restrict relays to those that are running

While looking at bandwidth data I realized that we often have "false positives" for relays that are long gone but are still shown because sbws is keeping measurement data for 28 days.

We should only show relays/take them into account for period X if they are running. "running" meaning here if at least one dir-auth thinks they are Running (so we can see their values even if they are not in the consensus currently).