Automatic merge from submit-queue (batch tested with PRs 56250, 56809, 56812, 56792, 56724). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Hit ILB endpoint in e2e test
**What this PR does / why we need it**:
During the ILB e2e networking test, a pod is created and curls the ILB's IP address, validating that the load balancer correctly routes traffic to the K8s service. Test will also hit the external LB endpoint after switching from ILB->ELB, validating no GCE conversion issues going from ILB to ELB.
This does not validate that the load balancer is accessible externally to the cluster (but on the same network).
**Release note**:
```release-note
NONE
```
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