Progress bar flickers after full sync

[casey]

When running ord server, the progress bar flashes repeatedly even when the server is fully synced. We should change it so it only draws the progress bar if there's more than 1 block to sync. (We could do more than 0 block to sync, but 0 or 1 blocks to sync is the common case, and one block should be so fast a progress bar isn't very useful.)