Automatic merge from submit-queue

Set NetworkInterfaces and Subnets to nil before updating Azure security groups

**What this PR does / why we need it**: This is a workaround until we have an upstream fix in azure-sdk-for-go/go-autorest. Corresponding issues are https://github.com/kubernetes/kubernetes/issues/40332 and https://github.com/Azure/go-autorest/issues/112

In k8s 1.5.2, an update to azure-sdk-for-go was cherry-picked, which broke creation/updating of LBs on Azure. As we should have it back to a working state ASAP, I'd like to do a workaround for now and later when the upstream fix comes in, remove the workaround again.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #40332

**Release note**:

```release-note
Fix failing load balancers in Azure
```

CC @colemickens