Update f_defaults.conf to support elasticsearch returner (#335)

Proposed pull request for elasticsearch returner in the minion.d/f_defaults.conf file

salt/files/minion.d/f_defaults.conf

 #event_match_type: startswith
 {{ get_config('event_match_type', 'startswith') }}
 
+{% if 'elasticsearch' in cfg_minion -%}
+{%- do default_keys.append('elasticsearch') %}
+{%- do default_keys.append('return') %}
+#####   elasticsearch connection settings  #####
+##########################################
+{%- for name, value in cfg_minion['elasticsearch'].items() %}
+{%- if value is list %}
+elasticsearch.{{ name }}:
+{%- for objvalue in value %}
+  - {{ objvalue }}
+{%- endfor %}
+{%- else %}
+elasticsearch.{{ name }}: {{ value }}
+{%- endif %}
+{%- endfor %}
+{%- endif %}
+
+
 {% if 'mongo' in cfg_minion -%}
 {%- do default_keys.append('mongo') %}
 #####   mongodb connection settings  #####