We should install python3-* instead of python2-* in CentOS8.
This change fixes the remaining usage of python2-* left for
netwokring-ansible and networking-baremetal.
This includes 260aa9fe29 which fixed
the wrong package names in unit tests.
(cherry picked from commit 34b5036ed8)
(cherry picked from commit ca26611290)
(cherry picked from commit b85b99dfac)
Currently we set both domain_name and domain_id for some configuration
files, but it makes it difficult for operators to use their original
domain because they should update both parameters correctly.
Because it's redundant to required both name and id set, this patch
deprecates all domain_id parameters, so that operator needs to set
their domain name, which is predictable, before creating actual domain.