* Fix errors in configure-multiple-schedulers.md
- Failed to push docker image
- Errors found in my-scheduler logs
```
...
E0515 06:36:28.180428 1 reflector.go:205] k8s.io/kubernetes/vendor/k8s.io/client-go/informers/factory.go:130: Failed to list *v1beta1.ReplicaSet: replicasets.extensions is forbidden: User "system:serviceaccount:kube-system:default" cannot list replicasets.extensions at the cluster scope
```
* Replace double quote with backticks for code strings
* Use `system:kube-scheduler` instead of `cluster-admin`
* Create dedicated service account for `my-scheduler`
Yujun Zhang