Change Neutron's default ML2 driver to OVN

As part of the Victoria PTG the Neutron community [0] agreed on changing
the default backend driver from ML2/OVS to ML2/OVN in DevStack. A lot of
changes have been submitted towards this goal including but not limted
to:

* Moving the OVN module to DevStack:
  https://review.opendev.org/c/openstack/devstack/+/734621

* Updating the OVN module to use distro packages instead of compiling
  OVN from source: https://review.opendev.org/c/openstack/devstack/+/763402o

And now this patch is changing the the actual Q_AGENT,
Q_ML2_TENANT_NETWORK_TYPE and Q_ML2_PLUGIN_MECHANISM_DRIVERS values in
devstack to what is expected by OVN as well as updating the Zuul
templates to enable the OVN services.

[0] https://etherpad.opendev.org/p/neutron-victoria-ptg

Change-Id: I92054ce9d2ab7a42746ed5dececef583b0f8a833
Signed-off-by: Lucas Alvares Gomes <lucasagomes@gmail.com>

.zuul.yaml

@@ -468,6 +468,10 @@
         SWIFT_HASH: 1234123412341234
         DEBUG_LIBVIRT_COREDUMPS: true
         NOVA_VNC_ENABLED: true
+        OVN_L3_CREATE_PUBLIC_NETWORK: true
+        OVN_DBS_LOG_LEVEL: dbg
+        ENABLE_CHASSIS_AS_GW: true
+        Q_USE_PROVIDERNET_FOR_PUBLIC: true
       devstack_local_conf:
         post-config:
           $NEUTRON_CONF:
@@ -477,7 +481,11 @@
         # Core services enabled for this branch.
         # This list replaces the test-matrix.
         # Shared services
-        dstat: true
+        #
+        # NOTE(lucasagomes): disable dstat until bug
+        # https://bugs.launchpad.net/ubuntu/+source/dstat/+bug/1866619 is
+        # fixed. Also see: https://bugs.launchpad.net/neutron/+bug/1898863
+        dstat: false
         etcd3: true
         memory_tracker: true
         mysql: true
@@ -496,13 +504,14 @@
         n-sch: true
         # Placement service
         placement-api: true
+        # OVN services
+        ovn-controller: true
+        ovn-northd: true
+        ovs-vswitchd: true
+        ovsdb-server: true
         # Neutron services
-        q-agt: true
-        q-dhcp: true
-        q-l3: true
-        q-meta: true
-        q-metering: true
         q-svc: true
+        q-ovn-metadata-agent: true
         # Swift services
         s-account: true
         s-container: true
@@ -527,15 +536,24 @@
           # Core services enabled for this branch.
           # This list replaces the test-matrix.
           # Shared services
-          dstat: true
+          #
+          # NOTE(lucasagomes): disable dstat until bug
+          # https://bugs.launchpad.net/ubuntu/+source/dstat/+bug/1866619 is
+          # fixed. Also see: https://bugs.launchpad.net/neutron/+bug/1898863
+          dstat: false
           memory_tracker: true
           tls-proxy: true
           # Nova services
           n-cpu: true
           # Placement services
           placement-client: true
+          # OVN services
+          ovn-controller: true
+          ovn-northd: false
+          ovs-vswitchd: true
+          ovsdb-server: true
           # Neutron services
-          q-agt: true
+          q-ovn-metadata-agent: true
           # Cinder services
           c-bak: true
           c-vol: true
@@ -549,6 +567,7 @@
           # integrated gate, so specifying the services has not effect.
           # ceilometer-*: false
         devstack_localrc:
+          ENABLE_CHASSIS_AS_GW: false
           # Subnode specific settings
           GLANCE_HOSTPORT: "{{ hostvars['controller']['nodepool']['private_ipv4'] }}:9292"
           Q_HOST: "{{ hostvars['controller']['nodepool']['private_ipv4'] }}"

lib/neutron_plugins/ml2

@@ -8,14 +8,14 @@ _XTRACE_NEUTRON_ML2=$(set +o | grep xtrace)
 set +o xtrace
 
 # Default openvswitch L2 agent
-Q_AGENT=${Q_AGENT:-openvswitch}
+Q_AGENT=${Q_AGENT:-ovn}
 if [ -f $TOP_DIR/lib/neutron_plugins/${Q_AGENT}_agent ]; then
     source $TOP_DIR/lib/neutron_plugins/${Q_AGENT}_agent
 fi
 
 # Enable this to simply and quickly enable tunneling with ML2.
 # Select either 'gre', 'vxlan', or 'gre,vxlan'
-Q_ML2_TENANT_NETWORK_TYPE=${Q_ML2_TENANT_NETWORK_TYPE:-"vxlan"}
+Q_ML2_TENANT_NETWORK_TYPE=${Q_ML2_TENANT_NETWORK_TYPE:-"geneve"}
 # This has to be set here since the agent will set this in the config file
 if [[ "$Q_ML2_TENANT_NETWORK_TYPE" == "gre" || "$Q_ML2_TENANT_NETWORK_TYPE" == "vxlan" ]]; then
     Q_TUNNEL_TYPES=$Q_ML2_TENANT_NETWORK_TYPE
@@ -24,7 +24,7 @@ elif [[ "$ENABLE_TENANT_TUNNELS" == "True" ]]; then
 fi
 
 # List of MechanismDrivers to load
-Q_ML2_PLUGIN_MECHANISM_DRIVERS=${Q_ML2_PLUGIN_MECHANISM_DRIVERS:-openvswitch,linuxbridge}
+Q_ML2_PLUGIN_MECHANISM_DRIVERS=${Q_ML2_PLUGIN_MECHANISM_DRIVERS:-ovn}
 # Default GRE TypeDriver options
 Q_ML2_PLUGIN_GRE_TYPE_OPTIONS=${Q_ML2_PLUGIN_GRE_TYPE_OPTIONS:-tunnel_id_ranges=$TENANT_TUNNEL_RANGES}
 # Default VXLAN TypeDriver options