The DHCP server should not announce any DNS resolver at all on the
subnet if "0.0.0.0" (IPv4) or "::" (IPv6) are configured as DNS
name servers in any subnet.
https://docs.openstack.org/neutron/latest/admin/config-dns-res.html
Conflicts:
neutron/common/ovn/utils.py
neutron/tests/unit/common/ovn/test_utils.py
Closes-Bug: #1950686
Change-Id: I78dd012764c7bd7a29aeb8d97c00b627d7723aeb
(cherry picked from commit a416f8b0ab)
(cherry picked from commit 625fa3a5b2)