NO-JIRA: fix TestPrometheusRemoteWrite to align the image used for the remote write receiver with k8s'

instead of the operator's upstream default image

This broke once prometheus-operator's default image is a prom 3
see openshift/prometheus-operator#321 (comment)

Author: machine424

test/e2e/framework/prometheus.go

@@ -32,7 +32,7 @@ import (
 	"k8s.io/apimachinery/pkg/util/intstr"
 )
 
-func (f Framework) MakePrometheusWithWebTLSRemoteReceive(name, tlsSecretName string) *monitoringv1.Prometheus {
+func (f Framework) MakePrometheusWithWebTLSRemoteReceive(name, tlsSecretName string, image *string) *monitoringv1.Prometheus {
 	// This is not required in the Prometheus spec, but we inspect that value in
 	// WaitForPrometheus. Omitting it causes this code to derefence a nil.
 	replicas := int32(1)
@@ -47,6 +47,7 @@ func (f Framework) MakePrometheusWithWebTLSRemoteReceive(name, tlsSecretName str
 		},
 		Spec: monitoringv1.PrometheusSpec{
 			CommonPrometheusFields: monitoringv1.CommonPrometheusFields{
+				Image:              image,
 				Replicas:           &replicas,
 				ServiceAccountName: "prometheus-k8s",
 				Secrets:            []string{tlsSecretName},

test/e2e/prometheus_test.go

@@ -123,6 +123,13 @@ type remoteWriteTest struct {
 func TestPrometheusRemoteWrite(t *testing.T) {
 	ctx := context.Background()
 
+	// Get the Prometheus image to use, use the same than k8s's.
+	k8sProm, err := f.MonitoringClient.Prometheuses(f.Ns).Get(ctx, "k8s", metav1.GetOptions{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	image := k8sProm.Spec.Image
+
 	name := "rwe2e"
 
 	// deploy a service for our remote write target
@@ -291,7 +298,7 @@ func TestPrometheusRemoteWrite(t *testing.T) {
 
 		t.Run(tc.name, func(t *testing.T) {
 			// deploy remote write target
-			prometheusReceiver := f.MakePrometheusWithWebTLSRemoteReceive(name, secName)
+			prometheusReceiver := f.MakePrometheusWithWebTLSRemoteReceive(name, secName, image)
 			if err := f.OperatorClient.CreateOrUpdatePrometheus(ctx, prometheusReceiver); err != nil {
 				t.Fatal(err)
 			}