remove 400 and 404 for get nodes endpoint and add 503 for secret update

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

api/swagger.yaml

@@ -6815,14 +6815,6 @@ paths:
             type: "array"
             items:
               $ref: "#/definitions/Node"
-        400:
-          description: "bad parameter"
-          schema:
-            $ref: "#/definitions/ErrorResponse"
-        404:
-          description: "no such node"
-          schema:
-            $ref: "#/definitions/ErrorResponse"
         500:
           description: "server error"
           schema:
@@ -7917,6 +7909,10 @@ paths:
           description: "server error"
           schema:
             $ref: "#/definitions/ErrorResponse"
+        503:
+          description: "node is not part of a swarm"
+          schema:
+            $ref: "#/definitions/ErrorResponse"
       parameters:
         - name: "id"
           in: "path"