Use metadata server grouping as default

Metadata seems like a better way to group instances for autoscaling, so
switch metadata to be the default option. Note that stable/2024.2 and
older versions don't support metadata grouping, so the jobs are defined
to use prefix grouping instead.

Change-Id: Id1c62255e58e9ceeffad2512a3e8e083c3d13f8b
diff --git a/.zuul.yaml b/.zuul.yaml
index 6ad9ff1..c900f24 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -63,6 +63,18 @@
     required-projects:
       - name: gnocchixyz/gnocchi
         override-checkout: stable/4.6
+    vars: &prefix_grouping_vars
+      devstack_local_conf:
+        test-config:
+          $TEMPEST_CONFIG:
+            service_available:
+              sg_core: True
+            telemetry_services:
+              metric_backends: gnocchi,prometheus
+            telemetry:
+              disable_ssl_certificate_validation: True
+              ceilometer_polling_interval: 15
+              autoscaling_instance_grouping: prefix
 
 - job:
     name: telemetry-dsvm-integration-2024-1
@@ -71,6 +83,7 @@
     required-projects:
       - name: gnocchixyz/gnocchi
         override-checkout: stable/4.6
+    vars: *prefix_grouping_vars
 
 - job:
     name: telemetry-dsvm-integration-2023-2
@@ -97,6 +110,7 @@
             telemetry:
               disable_ssl_certificate_validation: True
               ceilometer_polling_interval: 15
+              autoscaling_instance_grouping: prefix
 
 - job:
     name: telemetry-dsvm-integration
@@ -107,6 +121,7 @@
     required-projects:
       - name: gnocchixyz/gnocchi
         override-checkout: stable/4.6
+    vars: *prefix_grouping_vars
 
 - job:
     name: telemetry-dsvm-integration
@@ -162,6 +177,7 @@
     required-projects:
       - name: gnocchixyz/gnocchi
         override-checkout: stable/4.6
+    vars: *prefix_grouping_vars
 
 - job:
     name: telemetry-dsvm-integration-ipv6-only