storage test: verify that VDI.attach, VDI.detach works
storage test: verify that VDI.attach, VDI.detach works

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

xapi-project/message-switch,djs55/xcp-idl,Chunjie/xcp-idl,xapi-project/message-switch,johnelse/xcp-idl,xapi-project/message-switch,euanh/xcp-idl