[Fix #520] Refining before release

Signed-off-by: Francisco Javier Tirado Sarti <[email protected]>

impl/core/src/main/java/io/serverlessworkflow/impl/WorkflowInstance.java

@@ -68,7 +68,7 @@ private JsonNode whenCompleted(JsonNode node) {
             .map(f -> f.apply(workflowContext, null, node))
             .orElse(node);
     workflowContext.definition().outputSchemaValidator().ifPresent(v -> v.validate(output));
-    status.set(WorkflowStatus.COMPLETED);
+    status.compareAndSet(WorkflowStatus.RUNNING, WorkflowStatus.COMPLETED);
     completedAt = Instant.now();
     return output;
   }