Migrate CI jobs to Ubuntu Focal

Jobs for master branch are moved to be run on Ubuntu Focal.
All jobs for Stein, Train and Ussuri will be still run on Ubuntu
Bionic.

We also need to switch to legacy ebtables implementation in the
linuxbridge job because ebtables-nft implementation don't
supports syntax for source and destination ipv4 address in arp
tables. Please check bug [1] for more details.

Additionally scenario tests for port forwarding are now marked as
unstable as we have some problem with port forwarding on Ubuntu Focal.
See [2] for details.

Also test test_floating_ip_update is now marked as unstable as it is
failing pretty often on Ubuntu Focal. See [3] for details.

This patch also changes ovn hash used to be installed on the nodes
in the ovn scenario job with Ussuri release as this job is still run
on Ubuntu Bionic and we need to bump this hash there.

This patch additionally switches neutron-tempest-plugin-bgpvpn-bagpipe
jobs for master and ussuri to be non-voting due to bug [4].

This patch also switches neutron-tempest-plugin-designate-scenario
to be non-voting due to the bug [5]

[1] https://bugs.launchpad.net/neutron/+bug/1889779
[2] https://bugs.launchpad.net/neutron/+bug/1896735
[3] https://bugs.launchpad.net/neutron/+bug/1897326
[4] https://bugs.launchpad.net/networking-bagpipe/+bug/1897408
[5] https://bugs.launchpad.net/neutron/+bug/1891309

Related-Bug: #1896735

Change-Id: I9252b6a8786c43524ba0ebaa59b480ef8e489ff1
diff --git a/zuul.d/master_jobs.yaml b/zuul.d/master_jobs.yaml
index 45862c8..2c4fc02 100644
--- a/zuul.d/master_jobs.yaml
+++ b/zuul.d/master_jobs.yaml
@@ -158,6 +158,9 @@
     name: neutron-tempest-plugin-scenario-linuxbridge
     parent: neutron-tempest-plugin-scenario
     timeout: 10000
+    roles:
+      - zuul: openstack/neutron
+    pre-run: playbooks/linuxbridge-scenario-pre-run.yaml
     vars:
       network_api_extensions: *api_extensions
       devstack_localrc:
@@ -202,10 +205,6 @@
         ENABLE_CHASSIS_AS_GW: true
         OVN_L3_CREATE_PUBLIC_NETWORK: true
         OVN_DBS_LOG_LEVEL: dbg
-        # TODO(mjozefcz): Stop compiling OVS modules when meter action in kernel
-        # will be released in Ubuntu Bionic.
-        # More info: https://mail.openvswitch.org/pipermail/ovs-discuss/2018-December/048009.html
-        OVN_BUILD_MODULES: True
         ENABLE_TLS: True
         OVN_IGMP_SNOOPING_ENABLE: True
       devstack_services: