fixed naming of _mapping/field where its field not fields

changing the apache config to _mapping/fields leaded to the error: "Error No index found at http://server.example.de:5601/logstash-2014.02.04,logstash-2014.02.03/_mapping. Please create at least one index.If you're using a proxy ensure it is configured correctly."

Changing that to _mapping/field (without the s) fixed the problem. Tried to find all occurences of field(s) to be fixed