Kodi doesn't exit correctly because several classes are left in memory.

*I'm submitting a ...*
- [X] bug report
- [ ] feature request
- [ ] support request

## General information

I'm running kodi 18 in raspbian strech in a raspberry pi b 3

### Prerequisites

* [X] Are you running the latest version?
0.13.13

### Description

[Description of the bug or feature]

Kodi don't exit correctly because several classes are left in memory.

### Steps to Reproduce

1. [First Step]
Install the plugin version 0.13.13
2. [Second Step]
Exit Kodi

**Expected behavior:** [What you expected to happen]
Exit kodi to terminal

**Actual behavior:** [What actually happened]
Black screen or text with legend "Exiting Kodi"

## Context (Environment)
I was able to compile and install kodi 18.0.BETA3 in raspbian stretch and install it some binary addons (inputstream.adaptive and inputstream.rtmp) in order to run this pluging.

### Installation

* [ ] I installed the plugin via zip from the Releases page
* [X] I´m using the Netflix Repo
* [ ] I´m using a different source (Please tell which)

### Operating System

* [ ] Linux (x86/x64)
* [ ] OSX (x86/x64)
* [ ] Windows (x86/x64)
* [X] Linux (ARM)
* [ ] Android

#### Additional informatin on the environment

I installed Retropie 4.4 which is based on Raspbian Stretch and compile Kodi 18 with the binary extra addons instead of the Kodi 17.3 available in this distribution.

## Debug log

00:56:54.373 T:1595925232 ERROR: EXCEPTION Thrown (PythonToCppException) : -->Python callback/script returned the following error<--
- NOTE: IGNORING THIS CAN LEAD TO MEMORY LEAKS!
Error Type:
Error Contents:
Traceback (most recent call last):
File "/home/pi/.kodi/addons/plugin.video.netflix/addon.py", line 33, in
NAVIGATION.router(paramstring=REQUEST_PARAMS)
File "/home/pi/.kodi/addons/plugin.video.netflix/resources/lib/utils.py", line 60, in wrapped
result = func(*args, **kwargs)
File "/home/pi/.kodi/addons/plugin.video.netflix/resources/lib/Navigation.py", line 123, in router
options = self.before_routing_action(params=params)
File "/home/pi/.kodi/addons/plugin.video.netflix/resources/lib/utils.py", line 60, in wrapped
result = func(*args, **kwargs)
File "/home/pi/.kodi/addons/plugin.video.netflix/resources/lib/Navigation.py", line 867, in before
_routing_action
'method': 'is_logged_in'}))
File "/home/pi/.kodi/addons/plugin.video.netflix/resources/lib/Navigation.py", line 1053, in call_
netflix_service
data = urllib2.urlopen(full_url).read()
File "/usr/lib/python2.7/urllib2.py", line 154, in urlopen
return opener.open(url, data, timeout)
File "/usr/lib/python2.7/urllib2.py", line 429, in open
response = self._open(req, data)
File "/usr/lib/python2.7/urllib2.py", line 447, in _open
'_open', req)
File "/usr/lib/python2.7/urllib2.py", line 407, in _call_chain
result = func(*args)
File "/usr/lib/python2.7/urllib2.py", line 1228, in http_open
return self.do_open(httplib.HTTPConnection, req)
File "/usr/lib/python2.7/urllib2.py", line 1198, in do_open
raise URLError(err)
URLError:
-->End of Python script error report<--
00:56:54.522 T:1595925232 WARNING: CPythonInvoker(3, /home/pi/.kodi/addons/plugin.video.netflix/addon.py): the python script "/home/pi/.kodi/addons/plugin.video.netflix/addon.py" has left several classes in memory that we couldn't clean up. The classes include: N9XBMCAddon9xbmcaddon5AddonE
00:56:54.526 T:1625289456 ERROR: GetDirectory - Error getting plugin://plugin.video.netflix/
00:56:54.553 T:1902452736 ERROR: CGUIMediaWindow::GetDirectory(plugin://plugin.video.netflix/) failed
00:57:45.039 T:1578099440 WARNING: CPythonInvoker(4, /home/pi/.kodi/addons/plugin.video.netflix/addon.py): the python script "/home/pi/.kodi/addons/plugin.video.netflix/addon.py" has left several classes in memory that we couldn't clean up. The classes include: N9XBMCAddon9xbmcaddon5AddonE

Start with addon.py and trace the calls through resources/lib/Navigation.py and resources/lib/utils.py shown in the log, especially the urllib2 connection failure and the reported cleanup warning. Reproduce the issue with plugin version 0.13.13 on Kodi 18 under Raspbian Stretch, then verify that Kodi exits to the terminal without the black screen or lingering-class warnings.

Written by the indexing model from the issue text.