Oof, use the "controller" node name in storprep, too

Now that we use the devstack nodeset, use its name.

Change-Id: I5bb5302ec15b510ebae7c4bcd1abcc559e804fbc
diff --git a/playbooks/sp-init.yaml b/playbooks/sp-init.yaml
index 779b16d..05914f8 100644
--- a/playbooks/sp-init.yaml
+++ b/playbooks/sp-init.yaml
@@ -1,7 +1,7 @@
 - hosts: localhost
   connection: local
   vars:
-    host_id: "{{ hostvars['tempest']['nodepool']['external_id'] }}"
+    host_id: "{{ hostvars['controller']['nodepool']['external_id'] }}"
     storprep_filename: "/tmp/storprep-bootstrap-{{ host_id }}.sh"
   tasks:
     - name: ctrl-sp-whoami-hostname
@@ -24,7 +24,7 @@
       shell:
         cmd: ps awwfux
 
-- hosts: tempest
+- hosts: all
   tasks:
     - name: sp-examine-pwd
       shell: