##### SUMMARY
If you import a template with a xml/json file the linked templates of a templates ( so the child templates not the root ones ) aren't processed if you want to remove linked templates.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
zabbix_templates

##### ANSIBLE VERSION
```shell
ansible 2.9.2
  config file = /mnt/d/Code/gitlab/zabbix-servers/ansible/ansible.cfg
  configured module search path = ['/home/fism/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /mnt/d/Code/gitlab/zabbix-servers/venv/lib/python3.6/site-packages/ansible
  executable location = /mnt/d/Code/gitlab/zabbix-servers/venv/bin/ansible
  python version = 3.6.9 (default, Nov  7 2019, 10:44:02) [GCC 8.3.0]
```

##### OS / ENVIRONMENT
Zabbix 4.4.4 on RHEL7

##### STEPS TO REPRODUCE
Export a template (no matter if with Zabbix itself or ansible). Change the corresponding linked template section of a template and reimport it.

Exported with Zabbix:
```yaml
<zabbix_export>
    <version>4.4</version>
    <date>2020-01-23T13:25:32Z</date>
    <groups>
        <group>
            <name>Templates</name>
        </group>
    </groups>
    <templates>
        <template>
            <template>fisma</template>
            <name>fisma</name>
            <templates>
                <template>
                    <name>fismb</name>
                </template>
            </templates>
            <groups>
                <group>
                    <name>Templates</name>
                </group>
            </groups>
        </template>
    </templates>
</zabbix_export>
```

Change to this with removing all linked templates ( fismb in above example ).
```yaml
<zabbix_export>
    <version>4.4</version>
    <date>2020-01-23T13:25:32Z</date>
    <groups>
        <group>
            <name>Templates</name>
        </group>
    </groups>
    <templates>
        <template>
            <template>fisma</template>
            <name>fisma</name>
            <groups>
                <group>
                    <name>Templates</name>
                </group>
            </groups>
        </template>
    </templates>
</zabbix_export>
```

##### EXPECTED RESULTS
fismb should be unlinked from fisma.


##### ACTUAL RESULTS
fismb is still linked with fisma.
"""Filters out keys from XML template that may wary between exports (e.g date or version) and
        keys that are not imported via this module.
        It is advised that provided XML template exactly matches XML structure used by Zabbix"""
        
        parsed_xml_root = self.load_xml_template(template_xml.strip())
        keep_keys = ['graphs', 'templates', 'triggers', 'value_maps']
        
        for node in list(parsed_xml_root):
            if node.tag not in keep_keys:
                parsed_xml_root.remove(node)
        
        for template in list(parsed_xml_root.find('templates')):
            for element in list(template):
                if element.text is None and len(list(element)) == 0:
                    template.remove(element)
        
        xml_root_text = list(line.strip() for line in ET.tostring(parsed_xml_root, encoding='utf8', method='xml').decode().split('\n'))
        return ''.join(xml_root_text)
    def load_json_template(self, template_json):