Performance improvements

* Speed up serialization of hostvars by simply using the internal
  dictionary used for cached lookups
* Use blocking gets/puts on queues instead of spin locking
* Merge sequential implicitly created blocks

lib/ansible/playbook/helpers.py

@@ -52,7 +52,13 @@ def load_list_of_blocks(ds, play, parent_block=None, role=None, task_include=Non
                 variable_manager=variable_manager,
                 loader=loader
             )
-            block_list.append(b)
+            # Implicit blocks are created by bare tasks listed in a play withou
+            # an explicit block statement. If we have two implicit blocks in a row,
+            # squash them down to a single block to save processing time later.
+            if b._implicit and len(block_list) > 0 and block_list[-1]._implicit:
+                block_list[-1].block.extend(b.block)
+            else:
+                block_list.append(b)
 
     return block_list