openqa/dispatcher: improve 'extra arches' implementation

These bits were still named and described as if they were ppc64
specific, even though they actually cover aarch64 too. Also I
decided I don't like the implementation of cueing *directly* off
the infra deployment type here, it feels wrong. Instead let's
just make it work from a config variable, and set that variable
to false by default and true in group_vars/openqa-stg.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

roles/openqa/dispatcher/tasks/main.yml

@@ -9,6 +9,12 @@
 # - external_hostname
 ##       string - The public hostname of the openQA server (used in ResultsDB links)
 ##       default - ansible_nodename
+# - openqa_extraarches
+##      bool - when this is set, this instance will be configured to
+##             create jobs for 'extra' arches beyond x86_64 (currently
+##             ppc64 and aarch64). Only set it if this instance will
+##             have worker hosts for those arches
+##      default - false
 #
 # Optional vars
 # - wikitcms_token
@@ -99,12 +105,12 @@
   notify:
   - restart fedmsg-hub
 
-# For now, we want ppc64 jobs generated on staging but not prod (as we
-# have ppc64 workers for stg but not prod). So we have a WANTED file
-# for staging.
-- name: Install ppc64-imbued WANTED file if this is staging
-  copy: src=images.json.ppc64 dest=/etc/fedora-openqa/images.json
-  when: (deployment_type is defined) and (deployment_type == 'stg')
+# For now, we only have enough ppc64/aarch64 workers for one instance,
+# so we have a variant WANTED file that we deploy based on a config
+# variable.
+- name: Install extra arch WANTED images config if enabled
+  copy: src=images.json.extraarches dest=/etc/fedora-openqa/images.json
+  when: openqa_extraarches
   notify:
   - restart fedmsg-hub