Update log metrics config for Logstash downgrade

The format for the Logstash Kafka output plugin worker count is
integer in Logstash 2 and string in Logstash 5. Since we have downgraded
Logstash we need to switch formats here.

Change-Id: I98113dda05bbb44410916c27d7d3bcd59a034a98
Partially-Implements: blueprint monasca-roles

ansible/roles/monasca/templates/monasca-log-metrics/log-metrics.conf.j2

@@ -71,6 +71,6 @@ output {
         bootstrap_servers => "{{ monasca_kafka_servers }}"
         topic_id => "{{ monasca_metrics_topic }}"
         client_id => "log_metrics_{{ ansible_hostname }}"
-        workers => "{{ monasca_log_pipeline_threads }}"
+        workers => {{ monasca_log_pipeline_threads|int }}
     }
 }