i18n: improve labels for RNG

Use a separate string in case it has an associated device to avoid a
string puzzle.

Reviewed-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Pino Toscano <ptoscano@redhat.com>

virtManager/details/details.py

@@ -243,10 +243,9 @@ def _label_for_device(dev):
         return _("Controller") + (" %s %s" % (
                 vmmAddHardware.controller_pretty_desc(dev), dev.index))
     if devtype == "rng":
-        label = _("RNG")
         if dev.device:
-            label += (" %s" % dev.device)
-        return label
+            return _("RNG %(device)s") % {"device": dev.device}
+        return _("RNG")
     if devtype == "tpm":
         label = _("TPM")
         if dev.device_path: