Pass backendErr to emitMetrics

[s-fairchild]

nil was mistakenly being passed to emitMetrics, causing resultType to always fail collection due to the nil backendError provided.

Which issue this PR addresses:

Fixes ARO-10816

What this PR does / why we need it:

The backend error was not being passed to emitMetrics, nil was being provided instead.
This caused the resultType to always fail to collect, given that the error was always nil.

Example of this:

WARN[0000] failed to collect metric: resulttype          resource_group=resourcegroup resource_id=/subscriptions/00000000-0000-0000-0000-000000000000/resourcegroups/resourcegroup/providers/microsoft.redhatopenshift/openshiftclusters/resourcename resource_name=resourcename subscription_id=00000000-0000-0000-0000-000000000000

INFO[0000] backend.openshiftcluster.AdminUpdating: resulttype = empty  resource_group=resourcegroup resource_id=/subscriptions/00000000-0000-0000-0000-000000000000/resourcegroups/resourcegroup/providers/microsoft.redhatopenshift/openshiftclusters/resourcename resource_name=resourcename subscription_id=00000000-0000-0000-0000-000000000000

Test plan for issue:

Existing unit tests cover this.

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

No

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

The existing unit tests work correctly when the backendErr is provided, with a status code.

# Failure status code
INFO[0000] long running operation failed                 LOGKIND=asyncqos errorDetails="oh no!" operationType=AdminUpdating resource_group=resourcegroup resource_id=/subscriptions/00000000-0000-0000-0000-000000000000/resourcegroups/resourcegroup/providers/microsoft.redhatopenshift/openshiftclusters/resourcename resource_name=resourcename resultType=InternalServerError subscription_id=00000000-0000-0000-0000-000000000000

# Success status code
INFO[0000] long running operation succeeded              LOGKIND=asyncqos operationType=AdminUpdating resource_group=resourcegroup resource_id=/subscriptions/00000000-0000-0000-0000-000000000000/resourcegroups/resourcegroup/providers/microsoft.redhatopenshift/openshiftclusters/resourcename resource_name=resourcename resultType=Success subscription_id=00000000-0000-0000-0000-000000000000

[s-fairchild]

/azp run ci

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[hlipsig]

Good catch. Thanks.