Fix connectivity between octavia and amphorae.

After OSA AIO deploy octavia container and amphorae VMs are placed
in one L2 network domain but have different subnets, so it isn't possible
for octavia container to connect to amphorae VMs for configuration.
The solution is to create neutron subnet with the same CIDR as for
lbaas-mgmt, but separate pool from space where container will start

Change-Id: I477878073f8698862dd38b1249025e2f8c7a68ed
Closes-Bug: 1818441

etc/openstack_deploy/openstack_user_config.yml.aio.j2

@@ -18,6 +18,7 @@ used_ips:
 {% if 'octavia' in bootstrap_host_services %}
   - "172.29.252.1,172.29.252.50"
   - "172.29.252.100"
+  - "172.29.253.1,172.29.253.200"
 {% endif %}
   - "172.29.236.1,172.29.236.50"
   - "172.29.236.100"

tests/roles/bootstrap-host/templates/user_variables.aio.yml.j2

@@ -88,6 +88,10 @@ neutron_api_threads_max: 2
 neutron_api_threads: 2
 neutron_num_sync_threads: 1
 
+## Octavia
+octavia_management_net_subnet_cidr: 172.29.252.0/22
+octavia_management_net_subnet_allocation_pools: "172.29.253.1-172.29.253.200"
+
 ## Heat
 heat_api_workers: 1
 heat_api_threads_max: 2