This is an update that allows the iscsi volume to check if a iscsi device belongs to a mpio device

If it does belong to the device then we make sure we mount the mpio device instead of
the raw device.

Heuristics
Login into /dev/disk/by-path/iqn-example.com.2999 -> /dev/sde
Check if sde existsin in /sys/block/[dm-X]/slaves/xx
If it does mount /dev/[dm-x] which will look like /dev/mapper/mpiodevicename in mount

examples/iscsi has more details

pkg/volume/util/device_util.go

@@ -0,0 +1,31 @@
+/*
+Copyright 2016 The Kubernetes Authors All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+//DeviceUtil is a util for common device methods
+type DeviceUtil interface {
+	FindMultipathDeviceForDevice(disk string) string
+}
+
+type deviceHandler struct {
+	get_io IoUtil
+}
+
+//NewDeviceHandler Create a new IoHandler implementation
+func NewDeviceHandler(io IoUtil) DeviceUtil {
+	return &deviceHandler{get_io: io}
+}