exporter: query template var keeps refresh value..

on export if the value is not set to never. Otherwise the template
variable will not be populated with any values.""

public/app/features/dashboard/export/exporter.ts

@@ -103,7 +103,7 @@ export class DashboardExporter {
         templateizeDatasourceUsage(variable);
         variable.options = [];
         variable.current = {};
-        variable.refresh = 1;
+        variable.refresh = variable.refresh > 0 ? variable.refresh : 1;
       }
     }