feat(backup): set transfers before uploading backed up data

We need to explicitly set transfers before backup.
Otherwise, a backup running after restore would inherit
its transfers setting, which might not be desirable.
Future commits will also make this configurable
by a dedicated --transfers flag.

pkg/service/backup/worker_upload.go

@@ -35,6 +35,9 @@ func (w *worker) uploadHost(ctx context.Context, h hostInfo) error {
 	if err := w.setRateLimit(ctx, h); err != nil {
 		return errors.Wrap(err, "set rate limit")
 	}
+	if err := w.Client.RcloneSetTransfers(ctx, h.IP, h.Transfers); err != nil {
+		return errors.Wrapf(err, "set transfers on %s to %d", h.IP, h.Transfers)
+	}
 
 	dirs := w.hostSnapshotDirs(h)