CSV empty_value might not be available on master

[Mpdreamz]

#4597 introduces empty_value on master which is documented to be available as per: https://www.elastic.co/guide/en/elasticsearch/reference/master/csv-processor.html

However we did see an integration test failure pop up related to this:

https://dev.azure.com/azure3/elasticsearch-net/_build/results?buildId=3689&view=logs&j=70d57b1a-3bb3-5656-1da8-d847c6de6c92&t=1327d875-a30a-5de5-c423-74b851577e38

[xUnit.net 00:14:30.6164584]     Tests.Ingest.PutPipeline.PutPipelineApiTests.ReturnsExpectedIsValid [FAIL]
[2020-04-21T20:07:29,326][INFO ][o.e.x.s.a.r.TransportPutRoleAction] [xpack-node-7bea8e9200] added role [role-nest-initializer-96b8dc0e]
[2020-04-21T20:07:29,356][INFO ][o.e.x.s.a.r.TransportPutRoleAction] [xpack-node-7bea8e9200] added role [role-ois-baae57e0-role]
  X Tests.Ingest.PutPipeline.PutPipelineApiTests.ReturnsExpectedResponse [7s 187ms]
  Error Message:
   Tests.Framework.EndpointTests.ResponseAssertionException : Expected response.Acknowledged to be true, but found False.
Response Under Test:
Invalid NEST response built from a unsuccessful (400) low level call on PUT: /_ingest/pipeline/pipeline-1?pretty=true&error_trace=true
# Audit trail of this API call:
 - [1] BadResponse: Node: https://localhost:9200/ Took: 00:00:01.2789750
# OriginalException: Elasticsearch.Net.ElasticsearchClientException: Request failed to execute. Call: Status code 400 from: PUT /_ingest/pipeline/pipeline-1?pretty=true&error_trace=true. ServerError: Type: parse_exception Reason: "processor [csv] doesn't support one or more provided configuration parameters [empty_value]"
# Request:
{"description":"My test pipeline","processors":[{"append":{"field":"state","value":["Stable","VeryActive"]}},{"csv":{"field":"name","target_fields":["targetField1","targetField2"],"trim":true,"empty_value":"empty"}},{"convert":{"field":"numberOfCommits","target_field":"targetField","type":"string"}},{"date":{"field":"startedOn","formats":["dd/MM/yyyy hh:mm:ss"],"target_field":"timestamp","timezone":"Europe/Amsterdam"}},{"enrich":{"field":"name","policy_name":"enrich_processor_policy","target_field":"target_field"}},{"fail":{"message":"an error message"}},{"foreach":{"field":"tags","processor":{"uppercase":{"field":"_value.name"}}}},{"grok":{"field":"description","pattern_definitions":{"FAVORITE_DOG":"border collie","RGB":"RED|BLUE|GREEN"},"patterns":["my %{FAVORITE_DOG:dog} is colored %{RGB:color}"]}},{"gsub":{"field":"name","pattern":"-","replacement":"_"}},{"join":{"field":"branches","separator":","}},{"lowercase":{"field":"name"}},{"remove":{"field":["suggest"]}},{"rename":{"field":"leadDeveloper","target_field":"projectLead"}},{"set":{"field":"name","value":"foo"}},{"split":{"field":"description","separator":"."}},{"trim":{"field":"name"}},{"uppercase":{"field":"name"}},{"dot_expander":{"field":"field.withDots"}},{"script":{"source":"ctx.numberOfCommits++"}},{"urldecode":{"field":"description","ignore_missing":true}},{"attachment":{"field":"description","ignore_missing":true,"indexed_chars":100000,"properties":["title","author"]}},{"circle":{"field":"description","target_field":"arbitraryShape","ignore_missing":true,"error_distance":10.0,"shape_type":"shape"}},{"bytes":{"field":"description","ignore_missing":true}},{"dissect":{"field":"description","pattern":"%{clientip} %{ident} %{auth} [%{@timestamp}] \"%{verb} %{request} HTTP/%{httpversion}\" %{status} %{size}","ignore_missing":true,"append_separator":" "}},{"drop":{"if":"true"}},{"kv":{"field":"description","field_split":"_","ignore_missing":true,"value_split":" "}},{"kv":{"field":"description","field_split":"_","ignore_missing":true,"strip_brackets":true,"trim_key":"xyz","trim_value":"abc","value_split":" "}},{"set_security_user":{"field":"name"}},{"pipeline":{"name":"x"}}]}
# Response:
{
  "error" : {
    "root_cause" : [
      {
        "type" : "parse_exception",
        "reason" : "processor [csv] doesn't support one or more provided configuration parameters [empty_value]",
        "processor_type" : "csv",
        "stack_trace" : "org.elasticsearch.ElasticsearchParseException: processor [csv] doesn't support one or more provided configuration parameters [empty_value]\r\n\tat .... "
  },
  "status" : 400
}

[russcam]

This is now addressed in #4726