Fix merging of -datasource.json files

The merge was missing a new line at the end of the merge, so only
the first datasource was being put into the ConfigMap.

hack/grafana-dashboards-configmap-generator/bin/grafana_dashboards_generate.sh

@@ -199,6 +199,7 @@ addArrayToConfigMap() {
 
     # Dashboard foot
     test "$type" = "dashboard" && cat $DASHBOARD_FOOT_FILE
+    [ "$(tail -c 1 "$file")" ] && echo
   done
   echo "---"