title: Elasticsearch read_only_allow_delete auto setting
body: <p>I have problem with Elasticsearch. I tried the following:</p>
  
  <pre class="lang-bash prettyprint-override"><code> $ curl -XPUT -H "Content-Type: application/json" \
       http://localhost:9200/_all/_settings \
         -d '{"index.blocks.read_only_allow_delete": false}'
  </code></pre>
  
  <p>My settings:</p>
  
  <pre class="lang-json prettyprint-override"><code>"settings": {
    "index": {
      "number_of_shards": "5",
      "blocks": {
        "read_only_allow_delete": "true"
      },
      "provided_name": "new-index",
      "creation_date": "1515433832692",
      "analysis": {
        "filter": {
          "ngram_filter": {
            "type": "ngram",
            "min_gram": "2",
            "max_gram": "4"
          }
        },
        "analyzer": {
          "ngram_analyzer": {
            "filter": [
              "ngram_filter"
            ],
            "type": "custom",
            "tokenizer": "standard"
          }
        }
      },
      "number_of_replicas": "1",
      "uuid": "OSG7CNAWR9-G3QC75K4oQQ",
      "version": {
        "created": "6010199"
      }
    }
  }
  </code></pre>
  
  <p>When I check settings it looks fine, but only a few seconds (3-5) and it's still set to <code>true</code>. I can't add new elements and query anything, only <code>_search</code> and <code>delete</code>. </p>
  
  <p>Someone have any idea how to resolve this?</p>
  
  <p><strong>NOTE:</strong> I'm using Elasticsearch version: 6.1.1</p>