Automatic merge from submit-queue

AWS: SSL support for ELB listeners through annotations

In the API, ports have only either TCP or UDP as their protocols, but ELB distinguishes HTTPS->HTTP[S]? from SSL->(SSL|TCP). 

Per #24978, this is implemented through two separate annotations:

`service.beta.kubernetes.io/aws-load-balancer-ssl-cert=arn:aws:acm:us-east-1:123456789012:certificate/12345678-1234-1234-1234-123456789012`
`service.beta.kubernetes.io/aws-load-balancer-backend-protocol=(https|http|ssl|tcp)`

Mixing plain-text and encrypted listeners will be in a separate PR, implementing #24978's `aws-load-balancer-ssl-ports=LIST`