Fix jinja version 2.7 compatibility needed

This is needed for trusty nodes.

PROD-19818

Change-Id: Icbceef33d56f4edf3f02269c82fb0545e8407aad
diff --git a/fluentd/files/match/copy.conf b/fluentd/files/match/copy.conf
index f59b977..28c0435 100644
--- a/fluentd/files/match/copy.conf
+++ b/fluentd/files/match/copy.conf
@@ -2,10 +2,10 @@
   {%- for store in values.store %}
   <store>
   {%- with values=store %}
-    {%- set content %}
+    {%- macro include_content() %}
       {%- include 'fluentd/files/match/' + store.get('type') + '.conf' %}
-    {%- endset %}
-  {{ content | indent(2, False) }}
+    {%- endmacro %}
+  {{ include_content() | indent(2, False) }}
   {%- endwith %}
   </store>
   {%- endfor %}