Is this a request for help?:
Yes

Is this an ISSUE or FEATURE REQUEST? (choose one):
ISSUE

What version of acs-engine?:
0.12.1

Orchestrator and version (e.g. Kubernetes, DC/OS, Swarm)
Kubernetes 1.9.1

What happened:
Internal Load Balancer created and associated with availability set but no target network ip configurations
were added. Manually adding them in the portal is a functional workaround.

What you expected to happen:
Minimally, the target ip configuration of the load balancer endpoints should be added.

How to reproduce it (as minimally and precisely as possible):

1. Deploy acs kubernetes cluster with single master, single agentpool.
   Use "availabilityProfile": "AvailabilitySet"

2. Create Kubernetes service of type LoadBalancer, annotate with "service.beta.kubernetes.io/azure-load-balancer-internal=true"

3. Observe no target network ip configurations were added to the backend pool. Test to confirm that traffic does not flow as expected.

Anything else we need to know:
Deployed to custom vnet