libvirt: removing lxc specific disk mapping

Currently, LXC specific disk mapping is being created, preventing
the attached volumes from being added to the LXC disk mapping.
Removing this part, to allow volumes to be included in mapping.

Related-Bug: #1269990
Change-Id: I97bcff558b6d8876a10adb36c19ab3f4c972a708
Merge "libvirt: removing lxc specific disk mapping"