update example zuul job parent

The zuul job parent was not correct and if someone was following
the documentation importing or creating a new role, manually or
using the automation, their initial commit would not work. This
change updates the parent job name so that its functional on day
one.

Change-Id: Ic614d166451032c1b7b650a4d37a4e3a89afa629
Signed-off-by: Kevin Carter <kecarter@redhat.com>

doc/source/contributing.rst

@@ -23,7 +23,7 @@ When the role is ready for CI, add a **job** entry into the
         files:
         - ^tripleo_ansible/roles/${NEWROLENAME}/.*
         name: tripleo-ansible-centos-7-molecule-${NEWROLENAME}
-        parent: tripleo-ansible-centos
+        parent: tripleo-ansible-centos-7-base
         vars:
           tox_envlist: mol-${NEWROLENAME}
 

role-addition.yml

@@ -65,7 +65,7 @@
           {% if (job_index | length) < 1 %}
           {%   set new_job = {
                   "name": new_job_name,
-                  "parent": "tripleo-ansible-centos",
+                  "parent": "tripleo-ansible-centos-7-base",
                   "files": [
                     "^tripleo_ansible/roles/" ~ role_name ~ "/.*"
                   ],