Handle migration of br-ex network

[1] changing br-ex network from 192.168.24 to 172.16.1
for standalone jobs.

In order to allow the migration need to adjust
tempest configuration. This can be reverted once
[1] and [2] lands.

[1] https://review.opendev.org/#/c/757605
[2] https://review.opendev.org/#/c/755607

Related-Bug: #1895822
Change-Id: I1865db911661092debb133fd2638c9a6a9bd2e47

playbooks/tasks/tempest.yml

@@ -160,6 +160,36 @@
         tempest_network_ping_gateway: true
       when: tempest_cidr is defined
 
+    - name: Handle migration of br-ex network
+      block:
+        - name: Check if standalone parameters exists
+          stat:
+            path: "{{ working_dir }}/standalone_parameters.yaml"
+          register: parameter_file
+
+        - name: Read content of standalone parameters file if exists
+          slurp:
+            src: "{{ working_dir }}/standalone_parameters.yaml"
+          register: standalone_parameters
+          when: parameter_file.stat.exists
+
+        - name: Parse contents
+          set_fact:
+            standalone_parameters_yaml: "{{ standalone_parameters['content'] | b64decode | from_yaml }}"
+          when: parameter_file.stat.exists
+
+        - name: set tempest facts for br-ex network migration
+          set_fact:
+            tempest_public_subnet_cidr: '172.16.1.0/24'
+            tempest_public_subnet_gateway_ip: '172.16.1.2'
+            tempest_public_subnet_allocation_pools: '172.16.1.100-172.16.1.150'
+          when:
+            - parameter_file.stat.exists
+            - "'NeutronPhysicalBridge' not in (standalone_parameters_yaml | from_yaml)['parameter_defaults']"
+      when:
+        - job.environment_type is defined and job.environment_type == "standalone"
+        - job.bridge_address_prefix is defined and job.bridge_address_prefix == "172.16.1"
+
     - name: Set tempest workspace related vars
       set_fact:
         tempest_use_tempestconf: true