Increase min required libvirt to 0.9.11

Increase the min required libvirt version to 0.9.11 since
we require that for libvirt-python from PyPI to build
successfully. Kill off the legacy CPU model configuration
and legacy OpenVSwitch setup code paths only required by
libvirt < 0.9.11

Closes-Bug: #1254727
DocImpact
Change-Id: Ibe8d2117e1246e4097d1bedeadcd6d99618f8400
Merge "Increase min required libvirt to 0.9.11"