metrics: update status metrics label

Openshift overrides the `service` label for
all metrics in the cluster. Update the label
from `service` to `subsystem` for the status
metrics query. This helps us differentiate
between requests from composer and the worker
server.

internal/prometheus/status_metrics.go

@@ -14,7 +14,7 @@ func StatusRequestsCounter(subsystem string) *prometheus.CounterVec {
 		Namespace: Namespace,
 		Subsystem: subsystem,
 		Help:      "total number of http requests",
-	}, []string{"method", "path", "code", "service"})
+	}, []string{"method", "path", "code", "subsystem"})
 
 	err := prometheus.Register(counter)
 	if err != nil {