Pin manila-tempest-plugin in W and V CI jobs

manila-tempest-plugin needs to be pinned in Victoria and
Wallaby because the plugin requires newer tempest version
than is available there.

Change-Id: I4d1f7e68f354175665b7bc8849db14fc35e7c326

.zuul.yaml

@@ -104,6 +104,9 @@
     override-checkout: stable/wallaby
     vars:
       branch: stable/wallaby
+    required-projects: &manila-tempest-plugin-pin
+      - name: openstack/manila-tempest-plugin
+        override-checkout: 1.8.0
 
 - job:
     name: refstack-client-devstack-victoria
@@ -111,6 +114,7 @@
     override-checkout: stable/victoria
     vars:
       branch: stable/victoria
+    required-projects: *manila-tempest-plugin-pin
 
 - job:
     name: refstack-client-devstack-ussuri