lxc network configuration allows setting target container NIC name

LXC network devices can now be assigned a custom NIC device name on the
container side. For example, this is configured with:

    <interface type='network'>
      <source network='default'/>
      <guest dev="eth1"/>
    </interface>

In this example the network card will appear as eth1 in the guest.
lxc conf2xml: convert lxc.network.name for veth networks
Kill last strto{l,ll,d} scouts

There's no need to use it since we have this shiny functions
that even checks for conversion and overflow errors.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
examples: Introduce domtop

There's this question on the list that is asked over and over again.
How do I get {cpu, memory, ...} usage in percentage? Or its modified
version: How do I plot nice graphs like virt-manager does?

It would be nice if we have an example to inspire people. And that's
what domtop should do. Yes, it could be written in different ways, but
I've chosen this one as I think it show explicitly what users need to
implement in order to imitate virt-manager's graphing.

Note: The usage is displayed from host perspective. That is, how much
host CPUs the domain is using. But it should be fairly simple to
switch do just guest CPU usage if needed.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
doc: domain: Clarify that disk type 'lun' works with iSCSI too

Disk type 'lun' enables SCSI command passthrough for a disk. We stated
that it works only with "block" disks. Qemu supports it also when using
the iSCSI protocol.
qemu: snapshot: Forbid snapshots of iSCSI passthrough devices

As with the local SCSI passthrough devicesm qemu can't support snapshots
on those as the block ops are handled by the device. This is also true
for iSCSI backing of the disk. Remove the check for the local block
device and just forbid snapshot when the disk is of type 'lun'.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1073368