Bug fix - Add nil pointer check for LoadBalancerProfile in cluster metrics

[s-fairchild]

Which issue this PR addresses:

ARO-9146

Fixes

What this PR does / why we need it:

If the doc.OpenShiftCluster.Properties.NetworkProfile.LoadBalancerProfile is nil, checking for a nil doc.OpenShiftCluster.Properties.NetworkProfile.LoadBalancerProfile.ManagedOutboundIPs will cause a panic.
Relevant line from stack trace:

(*openShiftClusterBackend).gatherNetworkMetrics(0xc000a0cff0, 0x5c35fa0?, 0xc00109c600, 0x6?)\n\t/app/pkg/backend/metrics.go:221 +0x930\ngithub.com/Azure/ARO-RP/pkg/backend.

Checking for doc.OpenShiftCluster.Properties.NetworkProfile.LoadBalancerProfile first will stop a nil doc.OpenShiftCluster.Properties.NetworkProfile.LoadBalancerProfile.ManagedOutboundIPs from being de referenced.

Test plan for issue:

Covered by unit tests.
Will also create a UDR cluster with this document: https://github.com/Azure/ARO-RP/blob/master/docs/deploy-development-rp.md#run-the-rp-and-create-a-cluster

Is there any documentation that needs to be updated for this PR?

No.

How do you know this will function as expected in production?

Unit tests added pass a nil LoadBalancerProfile on this branch, while causing a panic on master.

[tsatam]

LGTM. It doesn't need to be done immediately within this PR, but as soon as we can, we should introduce a panic guard within this metrics function so that future nil pointer dereferences or other panics cannot halt execution on the backend.

[cadenmarchese]

/azp run ci,e2e

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[jhoreman]

Approved, thanks for this!

[anshulvermapatel]

LGTM

[SrinivasAtmakuri]

LGTM!

[sankur-codes]

/azp run e2e

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).