Fix Octavia to use keystone_admin_project variable

Project name shouldn't be static as user may override it with
keystone_admin_project

Change-Id: If41b9d8de17985d960104c8daf27ea7d706c27c0

ansible/roles/octavia/tasks/register.yml

@@ -14,7 +14,7 @@
     module_args:
       user: "{{ octavia_keystone_user }}"
       role: admin
-      project: admin
+      project: "{{ keystone_admin_project }}"
       auth: "{{ openstack_octavia_auth }}"
       endpoint_type: "{{ openstack_interface }}"
       cacert: "{{ openstack_cacert }}"