Add collect_statistics_interval, rates_mode in rabbitmq.config template

1. Add collect_statistics_interval and rates_mode configurations in
rabbitmq.config template which enables to define custom value for
those fields.
2. Add collect_statistics_interval and rates_mode defaults in
defaults/main.yml

This is a manual Cherry Pick from the master/mitaka change
Ie349528929398f53a9d87e7fc02e0c95c9d6d4f1

Change-Id: Ie349528929398f53a9d87e7fc02e0c95c9d6d4f1
Closes-bug: 1617516

playbooks/roles/rabbitmq_server/defaults/main.yml

@@ -72,3 +72,9 @@ rabbitmq_ssl_self_signed_subject: "/C=US/ST=Texas/L=San Antonio/O=IT/CN={{ conta
 # RabbitMQ erlang VM parameters
 rabbitmq_async_threads: 128
 rabbitmq_process_limit: 1048576
+
+# RabbitMQ collect statistics interval
+rabbitmq_collect_statistics_interval: 5000
+
+# RabbitMQ Management rates mode
+rabbitmq_management_rates_mode: basic

playbooks/roles/rabbitmq_server/templates/rabbitmq.config.j2

@@ -2,6 +2,7 @@
   {rabbit, [
     {loopback_users, []},
     {ssl_listeners, [5671]},
+    {collect_statistics_interval, {{ rabbitmq_collect_statistics_interval }} },
     {ssl_options, [{certfile,"{{ rabbitmq_ssl_cert }}"},
                    {keyfile,"{{ rabbitmq_ssl_key }}"},
                    {% if rabbitmq_user_ssl_ca_cert is defined -%}
@@ -11,5 +12,6 @@
                    {verify,verify_none},
                    {fail_if_no_peer_cert,false}]},
     {% if rabbitmq_cluster_partition_handling != 'ignore' %}{cluster_partition_handling, {{ rabbitmq_cluster_partition_handling }}}{% endif %}
-  ]}
+  ]},
+  {rabbitmq_management, [{rates_mode, {{ rabbitmq_management_rates_mode }} }] }
 ].