add status code 400 for api endpoint /events

Signed-off-by: allencloud <allen.sun@daocloud.io>

api/swagger.yaml

@@ -5383,6 +5383,10 @@ paths:
                   image: "alpine"
                   name: "my-container"
               time: 1461943101
+        400:
+          description: "bad parameter"
+          schema:
+            $ref: "#/definitions/ErrorResponse"
         500:
           description: "server error"
           schema:

docs/api/v1.24.md

@@ -2648,6 +2648,7 @@ Docker daemon report the following event:
 **Status codes**:
 
 -   **200** – no error
+-   **400** - bad parameter
 -   **500** – server error
 
 #### Get a tarball containing all images in a repository