Use correct libvirtd-bin group in Debian

While Ubuntu and RedHat family use the libvirtd group, Debian
uses libvirt for running the libvirt daemon.

Change-Id: Iedbea8e1c46d78a897a193f8bed42755bf2dca61
Add missing engine option to getopt

The option to specify a virtualization engine was documented and coded,
but not added to the list of parameters that getopt accepted.

Change-Id: Ia7079222912c6abc84edc6af5d12789eb8015dfa
Added parted to the list of packages to install on debian family

Parted is not installed by default on Debian system, and provides the command
partprobe needed in disk-image-create.

Change-Id: Ie03173398e425d65a908f25a880538a4912494b2
Use qemu as virt engine when kvm not available

By default, kvm is always use as the hypervisor when booting the seed
image, regardless it is available of not.

Test if kvm is loaded. If not, change default hypervisor to qemu.

Change-Id: Ia68d2c0d37e68abc1932376a3757ffe94a9a6662
Merge "Use qemu as virt engine when kvm not available"
Add /usr/sbin and /sbin to $PATH route

Depending on the system configuration, /usr/sbin and /sbin can be not
available to the user executing the script, and failing to boot
the seed image due to the missing route to the arp command.

In Fedora, Ubuntu and Debian arp is located in /usr/sbin, meanwhile
in Centos it's located in /sbin .

Change-Id: I34be00348626205929329962d7e2998b4dca55f3