Add sdk function to stop a running endpoint

**Is your feature request related to a problem? Please describe.**
Currently, an endpoint can only be started and stopped from command line. We may face the issue that an endpoint is started from a login node of a cluster. After logging out and logging back on, we may wind up with being in a different login node. Then there is no way for us to stop the endpoint from command line.

**Describe the solution you'd like**
Have an sdk function to stop a running endpoint.