in NodeStage RPC call we have to map the
device to the node plugin and make sure the
the device will be mounted to the global path
in nodeUnstage request unmount the device from
global path and unmap the device
if the volume mode is block we will be creating
a file inside a stageTargetPath and it will be
considered as the global path
Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>
