Disable dynamic mapping update in testTransportBulkTasks (elastic#38073)

If a replica does not have a right mapping yet, we will retry the index
request on that replica; then the actual tasks is higher than the
expected tasks. Since elastic#31140 this happens more frequently for we no
longer require acking on the dynamic mapping of index requests.

Relates elastic#31140
Closes elastic#37893

server/src/test/java/org/elasticsearch/action/admin/cluster/node/tasks/TasksIT.java

@@ -291,14 +291,15 @@ public void testTransportBroadcastReplicationTasks() {
         }
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/37893")
     public void testTransportBulkTasks() {
         registerTaskManageListeners(BulkAction.NAME);  // main task
         registerTaskManageListeners(BulkAction.NAME + "[s]");  // shard task
         registerTaskManageListeners(BulkAction.NAME + "[s][p]");  // shard task on primary
         registerTaskManageListeners(BulkAction.NAME + "[s][r]");  // shard task on replica
         createIndex("test");
         ensureGreen("test"); // Make sure all shards are allocated to catch replication tasks
+        // ensures the mapping is available on all nodes so we won't retry the request (in case replicas don't have the right mapping).
+        client().admin().indices().preparePutMapping("test").setType("doc").setSource("foo", "type=keyword").get();
         client().prepareBulk().add(client().prepareIndex("test", "doc", "test_id")
             .setSource("{\"foo\": \"bar\"}", XContentType.JSON)).get();