No query error information is returned beyond 500 using elasticsearch.net and NEST

NEST/Elasticsearch.Net version: 2.4.6

Elasticsearch version: 2.4.1

Description of the problem including expected versus actual behavior: Sending in a query with an error returns a 500 response with no additional information. When using a simple browser post the full detail is returned allowing the problem to be solved.

Steps to reproduce:

1. Submit an aggregation date range query without providing the date field and only range data

[Mpdreamz]

Elasticsearch will return:

{
  "error" : {
    "root_cause" : [ {
      "type" : "aggregation_execution_exception",
      "reason" : "could not find the appropriate value context to perform aggregation [startDates]"
    } ],
    "type" : "search_phase_execution_exception",
    "reason" : "all shards failed",
    "phase" : "query",
    "grouped" : true,
    "failed_shards" : [ {
      "shard" : 0,
      "index" : "project",
      "node" : "dBN8eDolTL69Juu95v7Ugg",
      "reason" : {
        "type" : "aggregation_execution_exception",
        "reason" : "could not find the appropriate value context to perform aggregation [startDates]"
      }
    } ]
  },
  "status" : 500
}

And this is available on ServerError

response.IsValid.Should().BeFalse();
var serverError = response.ServerError;
serverError.Should().NotBeNull();
serverError.Status.Should().Be(500);
serverError.Error.Reason.Should().Be("all shards failed");
serverError.Error.RootCause.First().Reason.Should().Contain("[startDates]");

I've attached a commit to this issue that showcases this.