bound the search tasks creation wait

addresses
trinodb#28941 (comment)

Author: lovasoa

plugin/trino-elasticsearch/src/test/java/io/trino/plugin/elasticsearch/TestBackpressureRestHighLevelClientCancellation.java

@@ -120,13 +120,11 @@ void testCancelledSqlQueryCancelsEsSearch() throws Exception {
             QueryManager queryManager = (
                 (DistributedQueryRunner) getQueryRunner()
             ).getCoordinator().getQueryManager();
-            // Wait for the query to appear in ElasticSearch
-            while (getSearchTasks().isEmpty()) {
-                assertThat(future.isDone())
-                    .as("query should still be running")
-                    .isFalse();
+            // Wait for the query to appear in ElasticSearch (max 2s)
+            for (int i = 0; i < 20 && getSearchTasks().isEmpty(); i++) {
                 Thread.sleep(100);
             }
+            assertThat(getSearchTasks()).isNotEmpty();
 
             for (BasicQueryInfo info : queryManager.getQueries()) {
                 if (!info.getState().isDone()) {