enhancement(systemd_exporter): supports multiple web listen addresses in preflight

this is for consistency with the other roles' preflight asserts for when the
exporter itself finally supports multiple web listen addresses

Signed-off-by: Christian Krause <christian.krause@idiv.de>

roles/systemd_exporter/tasks/preflight.yml

@@ -20,10 +20,21 @@
   ansible.builtin.package_facts:
   when: "not 'packages' in ansible_facts"
 
+- name: Assert that used version supports listen address type
+  ansible.builtin.assert:
+    that:
+      - >-
+        systemd_exporter_web_listen_address is string
+
 - name: Naive assertion of proper listen address
   ansible.builtin.assert:
     that:
-      - "':' in systemd_exporter_web_listen_address"
+      - >-
+        [systemd_exporter_web_listen_address] |
+          flatten |
+          reject('match', '.+:\\d+$') |
+          list |
+          length == 0
 
 - name: Assert that TLS config is correct
   when: systemd_exporter_tls_server_config | length > 0