QoS: Remove broken libvirt-based host network QoS

Back when the current host network level QoSa was added, it was
thought that libvirt had a way of configuring and honoring the
Quality of Service definitions that we were giving it. Unfortunately
that was an unimplemented part of their api, which forced us to
design a new implementation with different semantics.

This patch removes most of the host based network QoS implementation
from the codebase to prepare vdsm for the following patches which
will use the new tc package to provide outbound host network QoS.

We need this backport, because new libvirt's (1.2.9) Network XML
returns exception when we try to pass QoS parameters to it.
Traceback:
  File "/usr/lib64/python2.7/site-packages/libvirt.py", line 3881, in
networkDefineXML
    if ret is None:raise libvirtError('virNetworkDefineXML() failed',
conn=self)
libvirtError: unsupported configuration: Unsupported network-wide
<bandwidth> element in network vdsm-test-network with forward
mode='bridge'

Change-Id: I7b82cc6b656fb6af8caa2940c9ee2d14287f3526
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/30198
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/34319
Tested-by: Petr Horáček <phoracek@redhat.com>