KeyError: 'delegate_to' lookup in sync module needs to be checked to see if defined for ad hoc

```
$ ansible skyl2 -m synchronize -a "src=./foo dest=~/bar/baz"
XX | FAILED => Traceback (most recent call last):
  File "ansible/lib/ansible/runner/__init__.py", line 394, in _executor
    exec_rc = self._executor_internal(host, new_stdin)
  File "ansible/lib/ansible/runner/__init__.py", line 485, in _executor_internal
    return self._executor_internal_inner(host, self.module_name, self.module_args, inject, port, complex_args=complex_args)
  File "ansible/lib/ansible/runner/__init__.py", line 578, in _executor_internal_inner
    handler.setup(module_name, inject)
  File "ansible/lib/ansible/runner/action_plugins/synchronize.py", line 39, in setup
    if inject['delegate_to'] is None:
KeyError: 'delegate_to'
```