Re-enable memory_tracker

The old peakmem_tracker service has been disabled in [0], now enable
the replacement memory_tracker.

Also fail when the old service is still configured, otherwise
consumers might never notice.

Depends-On: https://review.opendev.org/739995
Change-Id: I583caf3f36a8ff41d7d4106dabc6c5f24243085e

.zuul.yaml

@@ -404,6 +404,7 @@
         # Shared services
         dstat: true
         etcd3: true
+        memory_tracker: true
         mysql: true
         rabbit: true
     group-vars:
@@ -411,6 +412,7 @@
         devstack_services:
           # Shared services
           dstat: true
+          memory_tracker: true
         devstack_localrc:
           # Multinode specific settings
           HOST_IP: "{{ hostvars[inventory_hostname]['nodepool']['private_ipv4'] }}"
@@ -476,6 +478,7 @@
         # Shared services
         dstat: true
         etcd3: true
+        memory_tracker: true
         mysql: true
         rabbit: true
         tls-proxy: true
@@ -524,6 +527,7 @@
           # This list replaces the test-matrix.
           # Shared services
           dstat: true
+          memory_tracker: true
           tls-proxy: true
           # Nova services
           n-cpu: true

lib/dstat

@@ -35,10 +35,10 @@ function start_dstat {
     # to your localrc
     run_process memory_tracker "$TOP_DIR/tools/memory_tracker.sh" "" "root"
 
-    # remove support for the old name when it's no longer used (sometime in Queens)
+    # TODO(jh): Fail when using the old service name otherwise consumers might
+    # never notice that is has been removed.
     if is_service_enabled peakmem_tracker; then
-        deprecated "Use of peakmem_tracker in devstack is deprecated, use memory_tracker instead"
-        run_process peakmem_tracker "$TOP_DIR/tools/memory_tracker.sh" "" "root"
+        die $LINENO "The peakmem_tracker service has been removed, use memory_tracker instead"
     fi
 }