[TEST] setSimilarity in MinimumScoreCollectorTests

The test relies on scoring which does not hold if the similarity is
randomized when creating the IndexSearcher through the newSearcher utility
method.

Author: javanna

server/src/test/java/org/elasticsearch/common/lucene/MinimumScoreCollectorTests.java

@@ -22,6 +22,7 @@
 import org.apache.lucene.search.TopDocs;
 import org.apache.lucene.search.TopScoreDocCollector;
 import org.apache.lucene.search.TotalHitCountCollector;
+import org.apache.lucene.search.similarities.BM25Similarity;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.tests.index.RandomIndexWriter;
 import org.elasticsearch.core.IOUtils;
@@ -53,6 +54,7 @@ public void setUp() throws Exception {
         writer.flush();
         reader = writer.getReader();
         searcher = newSearcher(reader);
+        searcher.setSimilarity(new BM25Similarity());
         writer.close();
     }