Install zabbix on buster from debian sources

zabbix-repo/tasks/main.yml

@@ -6,6 +6,7 @@
   apt_key:
     data: "{{lookup('file', 'zabbix.gpg')}}"
     state: present
+  when: debian_version == "jessie" or debian_version == "stretch"
   notify:
     - update apt cache
   tags:
@@ -29,7 +30,7 @@
 - name: ensure apt knows about the current zabbix repo
   apt_repository:
     repo: "{{ item }}"
-    state: present
+    state: '{{"present" if debian_version == "jessie" or debian_version == "stretch" else "absent"}}'
   with_items:
     - 'deb http://repo.zabbix.com/zabbix/{{zabbix_version}}/debian {{ debian_version }} main'
     # yamllint disable-line rule:line-length