Fix pre pull of images in DiskPressure tests

This waits for DiskPressure to no longer exist before pre pulling images
after a DiskPressure test. Otherwise we risk to pull images, while
kubelet evicts/removes them.

test/e2e_node/system_node_critical_test.go

@@ -110,6 +110,13 @@ var _ = framework.KubeDescribe("SystemNodeCriticalPod [Slow] [Serial] [Disruptiv
 					return checkMirrorPodDisappear(f.ClientSet, mirrorPodName, ns)
 				}, time.Minute, time.Second*2).Should(gomega.BeNil())
 
+				ginkgo.By("making sure that node no longer has DiskPressure")
+				gomega.Eventually(func() error {
+					if hasNodeCondition(f, v1.NodeDiskPressure) {
+						return fmt.Errorf("Conditions havent returned to normal, node still has DiskPressure")
+					}
+					return nil
+				}, pressureDissapearTimeout, evictionPollInterval).Should(gomega.BeNil())
 			})
 		})
 	})