Docker shell module failed in the latest sonic-mgmt for some tasks

[msosyak]

Description
According to #1243, the fix #1253 was merged.
But this fix turned out to be incomplete and cause an error similar to previous when running some tasks with docker shell e.g. copy, template.

Here are the logs:

The full traceback is:
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/ansible/executor/task_executor.py", line 111, in run
    item_results = self._run_loop(items)
  File "/usr/local/lib/python2.7/dist-packages/ansible/executor/task_executor.py", line 371, in _run_loop
    res = self._execute(variables=task_vars)
  File "/usr/local/lib/python2.7/dist-packages/ansible/executor/task_executor.py", line 664, in _execute
    result = self._handler.run(task_vars=variables)
  File "/usr/local/lib/python2.7/dist-packages/ansible/plugins/action/copy.py", line 590, in run
    self._remove_tmp_path(self._connection._shell.tmpdir)
  File "/usr/local/lib/python2.7/dist-packages/ansible/plugins/action/__init__.py", line 398, in _remove_tmp_path
    cmd = self._connection._shell.remove(tmp_path, recurse=True)
  File "/var/user/jenkins/bfn-sonic-mgmt/ansible/shell_plugins/docker.py", line 44, in remove
    argv = self.get_option('ansible_python_interpreter').split()
  File "/usr/local/lib/python2.7/dist-packages/ansible/plugins/__init__.py", line 60, in get_option
    raise KeyError(to_native(e))
KeyError: 'Requested entry (plugin_type: shell plugin: docker setting: ansible_python_interpreter ) was not defined in configuration.'

fatal: [cab18-2-dut]: FAILED! => {
    "msg": "Unexpected failure during module execution.", 
    "stdout": ""
}

Steps to reproduce the issue:

1. run ecn_wred CT

Describe the results you received:

Describe the results you expected:

Additional information you deem important:

**Output of `show version`:**

```
(paste your output here)
```

**Attach debug file `sudo generate_dump`:


```
(paste your output here)
```

[msosyak]

Here is the fix for this issue: #1262
But it not looks like the best option which we can choose.
As I mentioned here #1253 (comment)
"maybe it is the time to look to the docker connection plugin."
So I've spent some time and created #1269 where I tried to use the docker connection plugin.

@qiluo-msft @lguohan Please have a look to #1269