Do not install libvirt python bindings from pip
Do not install libvirt python bindings from pip

Since [1] was merged, devstack no longer installs libvirt python
bindings from pip but use distro packages. This change removes
the logic to install the python bindings using pip to follow that
change in devstack, otherwise installation fails because of conflict
between packages available in pip and one installed by distro packages.

[1] https://review.opendev.org/c/openstack/devstack/+/798514

Closes-Bug: #1939990
Related-Bug: #1933096
Change-Id: I369a95cf30e91738d10ad2e5a3d5f6988bdd76cb

openstack/ceilometer,openstack/ceilometer