Since at least 12.04, the kvm package is a transitional dummy
package intended to move users to the newer qemu-kvm package. This
removes the dependency on this dummy package, which will be going away
in 14.04, and instead depends on the proper qemu-kvm package.
Change-Id: I4a88ada3cf32106413a9fae6fe77c9c4c28a524e
Closes-bug: #1294557
Moves installation and setup of libvirt to a common functions-libvirt,
which can be used by other drivers in the future that may require
cross-distro libvirt installation and config but are not using
VIRT_DRIVER=libvirt (ie, Ironic).
Change-Id: I4a9255c8b4bacd5acfde9b8061c9e537aeea592c
