Remove support for extensions as lists

With tempest devstack and networking-odl switched to using dict,
we can now remove support for using lists for the list of extensions.

Depends-on: https://review.openstack.org/539686/
Depends-on: https://review.openstack.org/539708/
Depends-on: https://review.openstack.org/539854/
Change-Id: I62aaa737300c3b24e416f18e4bc469e7bd46ea29

roles/stage-output/tasks/main.yaml

@@ -5,34 +5,18 @@
   register: sources
   no_log: true
 
-- name: Output a warning when input is not a dict and not empty
-  debug:
-    msg: "WARNING: extensions_to_txt is a list, values defined by parents will be overwritten"
-  when:
-    - extensions_to_txt is not mapping
-    - extensions_to_txt
-
-- name: Build the extensions list when input is not a dict (including empty)
+- name: Build the extensions list from a dict (or empty)
   set_fact:
     extension_list: >
-      {% set extensions = ['__does_not_match__'] -%}
+      {% set extensions = ['__do_not_match__'] -%}
       {% if extensions_to_txt -%}
-        {% set extensions = extensions_to_txt -%}
-      {% endif -%}
-      {{- extensions -}}
-  when: extensions_to_txt is not mapping
-
-- name: Build the extensions list when input is a dict
-  set_fact:
-    extension_list: >
-      {% set extensions = [] -%}
         {% for extension, extension_bool in extensions_to_txt.items() -%}
           {% if extension_bool -%}
             {% set _ = extensions.append(extension) -%}
           {% endif -%}
         {% endfor -%}
+      {% endif -%}
       {{- extensions -}}
-  when: extensions_to_txt is mapping
 
 - name: Build the extensions regular expression
   set_fact: