Fix Singel Value widget not rendering on tab switch (#819)

Signed-off-by: Daniel Valdivia <18384552+dvaldivia@users.noreply.github.com>

portal-ui/src/screens/Console/Dashboard/Prometheus/Widgets/SingleValueWidget.tsx

@@ -64,7 +64,7 @@ const SingleValueWidget = ({
   classes,
   apiPrefix,
 }: ISingleValueWidget) => {
-  const [loading, setLoading] = useState<boolean>(false);
+  const [loading, setLoading] = useState<boolean>(true);
   const [data, setData] = useState<string>("");
 
   useEffect(() => {