[libvirt] Add device operations support for libvirt (lxc)

Hello, Currently, libvirt is not support device operations for lxc. This is a patch that add device operations support for libvirt 0.10.2. 1. lxcDomainAttachDevice 2. lxcDomainAttachDeviceFlags 3. lxcDomainDetachDevice 4. lxcDomainDetachDeviceFlags 5. lxcDomainUpdateDeviceFlags In live mode, set devices.allow/deny to instance's cgroup and insert disk config into current domain. In config mode, just insert disk config into current domain. This is part of 'Fix up attach/detach volume for nova (openstack)'. Please see: https://bugzilla.redhat.com/show_bug.cgi?id=869259 -- Best regards! Heiher https://heiher.info