Tests: make sure that 2 segments are created in SearchCancellationTests

Otherwise, the test fails if forced merge kicks in.

core/src/test/java/org/elasticsearch/search/SearchCancellationTests.java

@@ -46,6 +46,7 @@ public class SearchCancellationTests extends ESTestCase {
     public static void before() throws IOException {
         dir = newDirectory();
         RandomIndexWriter w = new RandomIndexWriter(random(), dir);
+        w.setDoRandomForceMerge(false); // we need 2 segments
         indexRandomDocuments(w, TestUtil.nextInt(random(), 2, 20));
         w.flush();
         indexRandomDocuments(w, TestUtil.nextInt(random(), 1, 20));