fix(app/mustache): reuse mustache variables in templates [EE-3689] (#7286)

app/react/portainer/custom-templates/components/utils.ts

@@ -38,12 +38,15 @@ export function intersectVariables(
 ) {
   const oldVariablesWithLabel = oldVariables.filter((v) => !!v.label);
 
-  return [
+  return _.uniqBy(
+    [
       ...oldVariablesWithLabel,
       ...newVariables.filter(
         (v) => !oldVariablesWithLabel.find(({ name }) => name === v.name)
       ),
-  ];
+    ],
+    'name'
+  );
 }
 
 export function renderTemplate(