Ensure that e2e tests run on gce|gke and are appropriately

skipped for other cloud providers.

test/e2e/monitoring.go

@@ -42,7 +42,7 @@ var _ = Describe("Monitoring", func() {
 	})
 
 	It("verify monitoring pods and all cluster nodes are available on influxdb using heapster.", func() {
-		if testContext.Provider != "gce" {
+		if !providerIs("gce") {
 			By(fmt.Sprintf("Skipping Monitoring test, which is only supported for provider gce (not %s)",
 				testContext.Provider))
 			return