core: attach device ioTune map

Provide vdsm with device's ioTune data, when a disk has
disk profile and qos object.

for more info see: http://libvirt.org/formatdomain.html#elementsDisks

Change-Id: I515caa7ff8996711610a77a57d6683d2655545de
Bug-Url: https://bugzilla.redhat.com/1085049
Signed-off-by: Gilad Chaplik <gchaplik@redhat.com>