Merge "Address nit in NetworkStackUtils"

     * Look up the value of a property for a particular namespace from {@link DeviceConfig}.

     * @param namespace The namespace containing the property to look up.

     * @param name The name of the property to look up.

     * @param defaultValue The value to return if the property does not exist or has no non-null

     *                     value.

     * @param defaultValue The value to return if the property does not exist or has no valid value.

     * @return the corresponding value, or defaultValue if none exists.

     */

    @Nullable