Added error codes for exec resize in API docs

Signed-off-by: Thomas LEDOS <thomas.ledos92@gmail.com>
(cherry picked from commit 834272f978)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

api/swagger.yaml

@@ -8609,10 +8609,18 @@ paths:
       responses:
         200:
           description: "No error"
+        400:
+          description: "bad parameter"
+          schema:
+            $ref: "#/definitions/ErrorResponse"
         404:
           description: "No such exec instance"
           schema:
             $ref: "#/definitions/ErrorResponse"
+        500:
+          description: "Server error"
+          schema:
+            $ref: "#/definitions/ErrorResponse"
       parameters:
         - name: "id"
           in: "path"