roles/bind: Simplify zone allow-update settings

Items in the `allow_update` property can use the address match list
syntax to specify arbitrary restrictions, including TSIG key names.
There is really no need for a special case for key names.

roles/named/templates/named.zones.j2

@@ -7,11 +7,7 @@ zone "{{ zone.zone }}" {
 {% if zone.allow_update|d %}
     allow-update {
 {% for auth in zone.allow_update %}
-{% if auth.key is defined %}
-        key {{ auth.key }};
-{% else %}
         {{ auth }};
-{% endif %}
 {% endfor %}
     };
 {% endif %}