Extend ElasticsearchLuceneTestCase rather than LuceneTestCase

LuceneTestCase misses some thread filters that might fail a test
since a background cluster is still running from a previous test.
Upgrading analysis plugins fails

When an analysis plugins provides default index settings using `PreBuiltAnalyzerProviderFactory`,  `PreBuiltTokenFilterFactoryFactory` or `PreBuiltTokenizerFactoryFactory` it fails when upgrading it with elasticsearch superior or equal to 0.90.5.

Related issue: #4936

Fix is needed in core. But, in the meantime, analysis plugins developers can fix that issue by overloading default prebuilt factories.

For example:

```java
public class StempelAnalyzerProviderFactory extends PreBuiltAnalyzerProviderFactory {

    private final PreBuiltAnalyzerProvider analyzerProvider;

    public StempelAnalyzerProviderFactory(String name, AnalyzerScope scope, Analyzer analyzer) {
        super(name, scope, analyzer);
        analyzerProvider = new PreBuiltAnalyzerProvider(name, scope, analyzer);
    }

    @Override
    public AnalyzerProvider create(String name, Settings settings) {
        return analyzerProvider;
    }

    public Analyzer analyzer() {
        return analyzerProvider.get();
    }
}
```

And instead of:

```java
    @Inject
    public PolishIndicesAnalysis(Settings settings, IndicesAnalysisService indicesAnalysisService) {
        super(settings);
        indicesAnalysisService.analyzerProviderFactories().put("polish", new PreBuiltAnalyzerProviderFactory("polish", AnalyzerScope.INDICES, new PolishAnalyzer(Lucene.ANALYZER_VERSION)));
    }
```

do

```java
    @Inject
    public PolishIndicesAnalysis(Settings settings, IndicesAnalysisService indicesAnalysisService) {
        super(settings);
        indicesAnalysisService.analyzerProviderFactories().put("polish", new StempelAnalyzerProviderFactory("polish", AnalyzerScope.INDICES, new PolishAnalyzer(Lucene.ANALYZER_VERSION)));
    }
```

Closes #5030
s/\t/    /
[TEST] run REST tests against multiple nodes (round-robin)

Multiple nodes are now started when running REST tests against the `TestCluster` (default randomized settings are now used instead of the hardcoded `1`)

Added also randomized round-robin based on all available nodes, and ability to provide multiple addresses when running tests against an external cluster to have the same behaviour
[TEST] removed leftover delete alias test in delete mapping
[TEST] slightly sped up warmer tests by providing warmers during index creation
[TEST] disabled refresh for get_source realtime test