Fix flaky instance deletion test

In many cases, envtest.K8sDeleteWithRetry() will time out before an instance gets deleted. Switch to using envtest.K8sDeleteWithRetryNoWait() and check that the Instance was deleted in the core test assertion instead of in the helper method.

Change-Id: Iae8966b7a4e2be14bde0e8ef4a73d21322fd324b

oracle/controllers/inttest/instancetest/instance_test.go

@@ -239,7 +239,7 @@ func deleteInstance(ctx context.Context, instanceName, namespace string) {
 			Name:      instanceName,
 		},
 	}
-	testhelpers.K8sDeleteWithRetry(k8sEnv.K8sClient, ctx, client.ObjectKey{Name: instanceName, Namespace: namespace}, instance)
+	testhelpers.K8sDeleteWithRetryNoWait(k8sEnv.K8sClient, ctx, client.ObjectKey{Name: instanceName, Namespace: namespace}, instance)
 }
 
 func deleteDatabase(ctx context.Context, databaseName, namespace string) {