Restore "skipping: no hosts matched" message

In ansible@159aa26
the result of _get_serialized_branches when no hosts were matched
changed from [[]] to []. Thus, the v2_playbook_on_no_hosts_matched
callback would not fire. Change the check so we get the error message
again. Fixes ansible#17706

lib/ansible/executor/playbook_executor.py

@@ -142,12 +142,11 @@ def run(self):
 
                         break_play = False
                         # we are actually running plays
-                        for batch in self._get_serialized_batches(new_play):
-                            if len(batch) == 0:
-                                self._tqm.send_callback('v2_playbook_on_play_start', new_play)
-                                self._tqm.send_callback('v2_playbook_on_no_hosts_matched')
-                                break
-
+                        batches = self._get_serialized_batches(new_play)
+                        if len(batches) == 0:
+                            self._tqm.send_callback('v2_playbook_on_play_start', new_play)
+                            self._tqm.send_callback('v2_playbook_on_no_hosts_matched')
+                        for batch in batches:
                             # restrict the inventory to the hosts in the serialized batch
                             self._inventory.restrict_to_hosts(batch)
                             # and run it...