Move scenario variables under vars

This is so variables can be overridden in playbooks
that include bootstrap-aio.yml. Otherwise, the variables
specified at time of the role invocation will always take
precedence.

Change-Id: Ie2df5f4b18795edbc4abec1c348057106537f857

tests/bootstrap-aio.yml

@@ -21,8 +21,10 @@
     - role: "sshd"
     - role: "pip_install"
     - role: "bootstrap-host"
+  vars:
     openstack_confd_entries: "{{ confd_overrides[scenario] }}"
     bootstrap_host_scenario: "{{ scenario }}"
+    scenario: "{{ lookup('env','SCENARIO') | default('aio', true) }}"
     confd_overrides:
       aio:
         - name: aodh.yml.aio
@@ -60,8 +62,6 @@
         - name: neutron.yml.aio
         - name: nova.yml.aio
         - name: swift.yml.aio
-  vars:
-    scenario: "{{ lookup('env','SCENARIO') | default('aio', true) }}"
     sshd:
       ListenAddress:
         - 0.0.0.0