Fix #11588 Settings containing Python string formatting are not displayed correctly

`omero config get` uses `safePrint` to display values, which interpolated any Python string formatting, e.g.

```
$ omero config set A %s
$ omero config get A
{'program_name': '/Users/andreas/omero/openmicroscopy/dist/bin/omero'}
```

https://trac.openmicroscopy.org.uk/ome/ticket/11588