Automatic merge from submit-queue (batch tested with PRs 40345, 38183, 40236, 40861, 40900)

remove the create-external-load-balancer flag in cmd/expose.go

**What this PR does / why we need it**:
In cmd/expose.go there is a todo "remove create-external-load-balancer in code on or after Aug 25, 2016.", and now it's been a long time past. So I remove this flag and modify the test cases. 
Please check for this, thanks!

**Release note**:

```
remove the deprecated flag "create-external-load-balancer" and use --type="LoadBalancer" instead.
```