zuul: Switch Xenial jobs to Bionic

Xenial does not support anything newer than Queens so there is little
point having distro jobs for it. Lets switch to Bionic. Moreover, the
neutron plugins have been merged with the respective agents so we
need to get rid of these non-existing packages.

Change-Id: I4409fb86529b02efbfb82e71bf5a955651983b74

vars/ubuntu.yml

@@ -83,11 +83,9 @@ neutron_service_distro_packages:
 
 neutron_optional_ovs_distro_packages:
   - neutron-openvswitch-agent
-  - neutron-plugin-openvswitch-agent
 
 neutron_optional_lxb_distro_packages:
   - neutron-linuxbridge-agent
-  - neutron-plugin-linuxbridge-agent
 
 neutron_optional_fwaas_distro_packages:
   - python-neutron-fwaas

zuul.d/project.yaml

@@ -32,7 +32,7 @@
         - openstack-ansible-odl-sfc-ubuntu-xenial
         - openstack-ansible-opendaylight-bgpvpn-ubuntu-xenial:
             voting: false
-        - openstack-ansible-functional-distro_install-ubuntu-xenial
+        - openstack-ansible-functional-distro_install-ubuntu-bionic
           # NOTE(hwoarang) Centos7 is having some troubles with repo dependencies
           # so disabling until it's investigated.
         - openstack-ansible-functional-distro_install-centos-7:
@@ -46,5 +46,5 @@
         - openstack-ansible-opendaylight-ubuntu-xenial
         - openstack-ansible-ovs-nsh-ubuntu-xenial
         - openstack-ansible-odl-sfc-ubuntu-xenial
-        - openstack-ansible-functional-distro_install-ubuntu-xenial
+        - openstack-ansible-functional-distro_install-ubuntu-bionic
         - openstack-ansible-functional-distro_install-opensuse-423