Adjust default polling interval

The default polling interval was updated from 600 to 300 in ceilometer
itself[1] but the default value in the polling class wasn't updated.

This updates the default value in our module so that we use the value
consistent with what is maintained in ceilometer repo.

[1] fc086ba3b38683765eabcdb45613463d85cb38fa

Change-Id: I7bcbbebf093228b0885b2647d86e47e2b673e518

manifests/agent/polling.pp

@@ -61,7 +61,7 @@
 #
 # [*polling_interval*]
 #   (Optional) Number of seconds between polling cycle
-#   Defaults to 600 seconds, used only if manage_polling is true.
+#   Defaults to 300 seconds, used only if manage_polling is true.
 #
 # [*polling_meters*]
 #   (Optional) Array of strings with meters to add to
@@ -94,7 +94,7 @@ class ceilometer::agent::polling (
   $resource_update_interval        = $facts['os_service_default'],
   $resource_cache_expiry           = $facts['os_service_default'],
   Boolean $manage_polling          = false,
-  $polling_interval                = 600,
+  $polling_interval                = 300,
   Array[String[1]] $polling_meters = $::ceilometer::params::polling_meters,
   Optional[Hash]$polling_config    = undef,
   $batch_size                      = $facts['os_service_default'],

releasenotes/notes/update-default-polling_interval-7a956d2399cac9fa.yaml

@@ -0,0 +1,5 @@
+---
+upgrade:
+  - |
+    Default value of ``ceilometer::agent::polling::polling_interval`` has been
+    updated from 600 to 300.

spec/classes/ceilometer_agent_polling_spec.rb

@@ -197,7 +197,7 @@ describe 'ceilometer::agent::polling' do
         :content                 => '---
 sources:
     - name: some_pollsters
-      interval: 600
+      interval: 300
       meters:
         - cpu
         - cpu_l3_cache