Deprecate CeilometerWorkers

It seems it's been unused for a while, let's deprecate it.

Change-Id: I346b1f78189e6e5186e0297ac964d65bdd89afcf

environments/low-memory-usage.yaml

@@ -1,6 +1,5 @@
 # Lower the memory usage of overcloud.
 parameter_defaults:
-  CeilometerWorkers: 1
   CinderWorkers: 1
   GlanceWorkers: 1
   HeatWorkers: 1

puppet/services/ceilometer-base.yaml

@@ -126,6 +126,16 @@ parameters:
     type: string
     description: archive policy to use with gnocchi backend
 
+parameter_groups:
+- label: deprecated
+  description: |
+   The following parameters are deprecated and will be removed. They should not
+   be relied on for new deployments. If you have concerns regarding deprecated
+   parameters, please contact the TripleO development team on IRC or the
+   OpenStack mailing list.
+  parameters:
+  - CeilometerWorkers
+
 conditions:
   service_debug_unset: {equals : [{get_param: CeilometerDebug}, '']}
 

releasenotes/notes/deprecate-ceilometer-workers-72b01f4bc6423f48.yaml

@@ -0,0 +1,3 @@
+---
+deprecations:
+  - The CeilometerWorkers parameter, unused, is now deprecated.