Commit 43b74ccc15 enabled use of Python 3
based packages but not switched to use Python 3.
Some of images still contain Python 2. There are two reasons:
- Ceph (ceph-common depends on Py2)
- python3-ldappool on Ubuntu 18.04
In Ceph situation Py3 packages were added. For second one we can not do
anything - Py2 dependency got dropped in Ubuntu 18.10 version.
Removed neutron-server-plugin-networking-infoblox due to being not
maintained. Once https://review.opendev.org/#/c/657578/ get merged
someone may revert that part.
Implements: blueprint debian-ubuntu-python3
Depends-on: Ie2a1077f7def0743f1403341985e2109aa490026
Change-Id: Ibfe0c2b8be98db56c61f74fb0247488ab3749ef4