Remove unused function Xapi_vdi.cancel_task
Remove unused function Xapi_vdi.cancel_task

Signed-off-by: Thomas Sanders <c547603d2dd860735c4f0c043b1348f5c48c02f8@citrix.com>

srowe/xen-api,srowe/xen-api,euanh/xen-api,srowe/xen-api,srowe/xen-api,euanh/xen-api,euanh/xen-api,srowe/xen-api,euanh/xen-api,euanh/xen-api,euanh/xen-api