Revert "Use a service between e2e volume tests clients and servers."

iSCSI and RBD volumes don't work as Kubernetes services - these protocols
are broken by S-NAT created by kube-proxy - at least iSCSI exhanges real
IP address of the iSCSI target as part of the protocol.

This reverts commit 118004c166.

test/e2e/persistent_volumes.go

@@ -63,7 +63,8 @@ var _ = Describe("[Skipped] persistentVolumes", func() {
 			volumeTestCleanup(c, config)
 		}()
 
-		serverIP := startVolumeServer(c, config)
+		pod := startVolumeServer(c, config)
+		serverIP := pod.Status.PodIP
 		Logf("NFS server IP address: %v", serverIP)
 
 		pv := makePersistentVolume(serverIP)