Add ability to configure ES request_timeout

To configure it use:

parameters:
  fluentd:
    agent:
      config:
        label:
          default_output:
            match:
              elasticsearch_output:
                request_timeout: 60s

Change-Id: I09330f955b43e6234ec1fc36bde3ce2f65455bfe
diff --git a/fluentd/files/match/elasticsearch.conf b/fluentd/files/match/elasticsearch.conf
index e26a313..ff015c8 100644
--- a/fluentd/files/match/elasticsearch.conf
+++ b/fluentd/files/match/elasticsearch.conf
@@ -10,6 +10,7 @@
   logstash_prefix {{ values.get("es_index_name", "log") }}
   logstash_dateformat %Y%m%d
   flush_interval {{ values.get("flush_interval", "10s") }}
+  request_timeout {{ values.get("request_timeout", "10s") }}
 {%- if values.get("buffer") %}
   <buffer>
   {%- with values=values.get("buffer") %}