backuptarget: add default at provisioning time (again)

we clear the db in the tests. the tests run the setup again and again.
so, it's easier to add default values in provision time instead of
migration.

src/provision.js

@@ -86,6 +86,7 @@ async function setupTask(domain, auditSource) {
         await reverseProxy.ensureCertificate(location, {}, auditSource);
         await ensureDhparams();
         await dashboard.setupLocation(constants.DASHBOARD_SUBDOMAIN, domain, auditSource);
+        await backupTargets.addDefault(auditSource);
         setProgress('setup', 'Done'),
         await eventlog.add(eventlog.ACTION_PROVISION, auditSource, {});
     } catch (error) {