Remove libvirt from integration images

- the libvirt packages should be installed by chef, and not preseeded by the
  image

Change-Id: I37f182f8f3e7715c41e1ed0e0799386766bc8d66

bootstrap.sh

@@ -7,6 +7,9 @@ if [ -f /usr/bin/yum ] ; then
   sudo yum -y groupinstall "Development Tools"
   sudo yum -y install xz-devel zlib-devel
 
+  # workaround for integration. let chef install libvirt later
+  sudo yum -y remove libvirt libvirt-python
+
   # uninstall requests from pip
   sudo pip uninstall requests -y || true
 
@@ -25,6 +28,9 @@ elif [ -f /usr/bin/apt-get ]; then
   sudo apt-get update
   sudo apt-get -y install build-essential liblzma-dev zlib1g-dev
 
+  # workaround for integration. let chef install what it needs later
+  sudo apt-get -y purge libvirt0 libvirt-dev python-libvirt
+
   # install chefdk
   chefdk=chefdk_1.5.0-1_amd64.deb
   wget -nv -t 3 https://packages.chef.io/stable/ubuntu/16.04/$chefdk