[Remote Store] Fail index creation with error message if repository does not exist

[sachinpkale]

Is your feature request related to a problem? Please describe.
If we create a remote store enabled index without creating repository first, index creation fails but does not provide any reason to understand the failure.

curl -X PUT "localhost:9200/my-index-1?pretty" -H 'Content-Type: application/json' -d' 
{
  "settings": {
    "index": {
      "number_of_shards": 1,
      "number_of_replicas": 1,
      "replication": {
        "type": "SEGMENT"
      },
      "remote_store": {
        "enabled": true
      }
    }
  }
}
'

{
  "acknowledged" : true,
  "shards_acknowledged" : false,
  "index" : "my-index-1"
}

If repository does not exist, index creation should fail fast and should provide clear reason of failure.