Term filter parser too lenient

[spinscale]

The term filter parser does allow specifying more than one field without barfing and throwing an exception, resulting in a last one wins scenario.

Sample to reproduce

GET /foo/bar/_search
{
  "query": {
    "filtered": {
      "query": {
        "match_all": {}
      },
      "filter": {
        "term": {
          "field2": "bar",
          "field1": "foo"
        }
      }
    }
  }
}

This should throw an exception, once field2 has been found and is tried to be overwritten.

[clintongormley]

@javanna is this still relevant with the query refactoring branch?

[javanna]

yes it is still relevant, it's a fix that could be applied on master independently