zabbix-repo: Fix obsolete apt_key usage

While we’re at it:
- update Zabbix’ key (now without obsolete ciphers)
- remove superfluous handlers (apt_repository updates on its own)

zabbix-repo/handlers/main.yml

----
-
-- name: update apt cache
-  apt: update_cache=true

zabbix-repo/tasks/main.yml

@@ -3,12 +3,13 @@
 # but does not mitigate package signing
 
 - name: ensure apt got the key to verify the zabbix repo
-  apt_key:
-    data: "{{ lookup('file', 'zabbix.gpg') }}"
-    state: present
+  copy:
+    src: zabbix.gpg
+    dest: /etc/apt/trusted.gpg.d/zabbix.gpg
+    owner: root
+    group: root
+    mode: "0644"
   when: zabbix_external_repo
-  notify:
-    - update apt cache
   tags:
     - repos
     - zabbix
@@ -22,8 +23,6 @@
     - 'deb http://repo.zabbix.com/zabbix/{{ old_zabbix_version }}/debian {{ debian_version }} main'
     # yamllint disable-line rule:line-length
     - 'deb-src http://repo.zabbix.com/zabbix/{{ old_zabbix_version }}/debian {{ debian_version }} main'
-  notify:
-    - update apt cache
   tags:
     - repos
     - zabbix
@@ -38,8 +37,6 @@
     - 'deb http://repo.zabbix.com/zabbix/{{ zabbix_version }}/debian {{ debian_version }} main'
     # yamllint disable-line rule:line-length
     - 'deb-src http://repo.zabbix.com/zabbix/{{ zabbix_version }}/debian {{ debian_version }} main'
-  notify:
-    - update apt cache
   when:
     - ansible_distribution == "Debian"
   tags:
@@ -55,8 +52,6 @@
     - 'deb http://repo.zabbix.com/zabbix/{{ zabbix_version }}/ubuntu {{ ansible_distribution_release }} main'
     # yamllint disable-line rule:line-length
     - 'deb-src http://repo.zabbix.com/zabbix/{{ zabbix_version }}/ubuntu {{ ansible_distribution_release }} main'
-  notify:
-    - update apt cache
   when:
     - ansible_distribution == "Ubuntu"
   tags:
@@ -64,11 +59,12 @@
     - zabbix
 
 - name: ensure chr's key is present
-  apt_key:
-    data: "{{ lookup('file', 'chr.gpg') }}"
-    state: present
-  notify:
-    - update apt cache
+  copy:
+    src: chr.asc
+    dest: /etc/apt/trusted.gpg.d/chr.asc
+    owner: root
+    group: root
+    mode: "0644"
   tags:
     - repos
     - zabbix
@@ -80,8 +76,6 @@
     state: present
   with_items:
     - 'deb http://repository.chr.istoph.de/ubuntu xenial main'
-  notify:
-    - update apt cache
   tags:
     - repos
     - zabbix
@@ -116,5 +110,3 @@
 #   tags:
 #     - repos
 #     - zabbix
-
-- meta: flush_handlers