Icinga doc fix (#1495)

* Document it is a dictionary to reduce confusion.

* Add variable example

plugins/modules/monitoring/icinga2_host.py

@@ -102,7 +102,7 @@ options:
   variables:
     type: dict
     description:
-      - List of variables.
+      - Dictionary of variables.
 extends_documentation_fragment:
   - url
 '''
@@ -116,6 +116,8 @@ EXAMPLES = '''
     state: present
     name: "{{ ansible_fqdn }}"
     ip: "{{ ansible_default_ipv4.address }}"
+    variables:
+      foo: "bar"
   delegate_to: 127.0.0.1
 '''