no send / receive statistics in logs

Hello,

When a backup is done with the --progress option, we get the progress but also at the end a summary of how much was transferred and in how much time. Eg.:

```text
summary: 882 MiByte in 37.4sec - average of 23.6 MiB/s
```

But curiously this statistics is missing when merely using the -v option. When using btrbk as cron job, we won't have --progress (it actually does not work) so we miss that information which is quite important.