[feat] Add prompt about master needing internet access

When package updates go through the master node, that master needs internet access.
Therefore, prompt the user about this requirement.

Resolves #146

setup/so-setup

@@ -231,6 +231,9 @@ fi
 
 if [[ $is_distmaster || ( $is_sensor || $is_node ) && ! $is_eval ]]; then
 	whiptail_master_updates
+	if [[ $setup_type == 'network' && $MASTERUPDATES == 1 ]]; then
+		whiptail_master_updates_warning
+	fi
 fi
 
 if [[ $is_minion ]]; then