Geohash is not indexed unless the precision is 12

[clintongormley]

If the geohash_precision is set to anything except the default (12), and geohash_prefix is not true, the geohash is not indexed:

PUT my_index
{
  "mappings": {
    "my_type": {
      "properties": {
        "location": {
          "type": "geo_point",
          "geohash": true,
          "geohash_precision": 11
        }
      }
    }
  }
}


PUT my_index/my_type/1
{
  "location": {
    "lat": 41.12,
    "lon": -71.34
  }
}

GET my_index/_search?fielddata_fields=location.geohash

[nknize]

This is a silly mappings refactor mistake... the bigger issue is that we didn't have a test for catching this. I'll backport and make sure there's sufficient test coverage.

[nknize]

Merged #13649