request_func for remove_from_load_balancer (and friends)

- [x] Mangle `supervisor.SupervisorService`
- [x] Mangle `launch_server_v1.delete_server`
- [x] Mangle `launch_server_v1.remove_from_load_balancer`
Do we also want to assert something about the `region` and `lb_region`, since those are utilized in the code paths this gets passed to?