Put the Volume and Datapath plugins in different directories
Put the Volume and Datapath plugins in different directories

The Volume plugins will map to XenAPI SM objects, and the Datapath
plugins will be considered 'internal' for now.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@citrix.com>

xapi-project/message-switch,xapi-project/message-switch,xapi-project/message-switch