fixed trace logging hidden by check for isDebugEnabled
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
Add a aggregation test that uses `doc.score` to make sure we don't forget to set the Scorer.
Log warning in case of double release of the IndexSearcher instead of throwing an exception.
[TEST] Added cat.allocation and cat.aliases tests
[TESTS] Fixed cat.allocation tests to work with one node cluster
[TESTS] Make cat.allocation tests handle different disk sizes
[TEST] fixed cat/allocation REST tests
[TESTS] Looks like Java character classes require explicit \s
Wait for green in mlt tests
Removed 0.90.* deprecation and addition notifications

Closes #5052
[DOCS] Removed deprecated queries/filters from Java API docs
Doc fix explaining resynchronization with the Cancel command.

Added line explaining resync process to Reroute/Cancel command.

Closes #5025
Merge pull request #5055 from seang-es/fix/5025

Doc fix explaining resynchronization with the Cancel command.