409 status code result to create service

Added example 409 status code result to the create service endpoint.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

docs/reference/api/docker_remote_api_v1.24.md

@@ -3980,6 +3980,7 @@ Create a service
 
 - **201** – no error
 - **406** – server error or node is not part of a swarm
+- **409** – name conflicts with an existing object
 
 JSON Parameters:
 

docs/reference/api/docker_remote_api_v1.25.md

@@ -3980,6 +3980,7 @@ Create a service
 
 - **201** – no error
 - **406** – server error or node is not part of a swarm
+- **409** – name conflicts with an existing object
 
 JSON Parameters: