pkg/cvo/metrics: Serve cluster_version_available_updates when channel is set

Since 8b91189 (cvo: Add prometheus metrics to the CVO for current
update state, 2018-11-05, #45), cluster_version_available_updates is
only served when there are unconditionally-recommended updates and
retrieval is succeeding.  This makes it hard to understand at the
fleet level when:

  cluster_operator_conditions{name="version", condition="RetrievedUpdates", reason="VersionNotFound"} == 0

is because of a misconfigured channel, or a misbehaving Update
Service, or otherwise.  We should always export
cluster_version_available_updates whenever a channel is set, to make
it easier to isolate the “because the cluster-admin has somehow
selected a channel not compatible with their current version” (which
we can’t do much about other than keep serving our existing
CannotRetrieveUpdates alert) from the other possibilities (which we
might be able to do something about).

Author: wking

pkg/cvo/metrics.go

@@ -629,7 +629,7 @@ func (m *operatorMetrics) Collect(ch chan<- prometheus.Metric) {
 			ch <- g
 		}
 
-		if len(cv.Spec.Upstream) > 0 || len(cv.Status.AvailableUpdates) > 0 || resourcemerge.IsOperatorStatusConditionTrue(cv.Status.Conditions, configv1.RetrievedUpdates) {
+		if len(cv.Spec.Channel) > 0 {
 			upstream := "<default>"
 			if len(m.optr.updateService) > 0 {
 				upstream = string(m.optr.updateService)