Use separate plays for Host prep steps

Instead of using one task include per role in the same play, use
separate plays instead. This reduces the amount of task skipping that
Ansible has to do since each include only applies to a single role.

In a deployment with many roles, this will improve performance.

Change-Id: I01ef631ea3dad8b9c030d61ed0883a9af13616ad
(cherry picked from commit 493d1c62fd)

common/deploy-steps.j2

@@ -437,9 +437,10 @@ outputs:
               tags:
                 - overcloud
                 - pre_deploy_steps
+{%- for role in roles %}
 
-            - hosts: {{primary_role_name}}:overcloud
-              name: Host prep steps
+            - hosts: {{role.name}}
+              name: {{role.name}} Host prep steps
               gather_facts: no
               any_errors_fatal: yes
               vars:
@@ -450,13 +451,11 @@ outputs:
                   file: path=/var/lib/docker-puppet state=directory setype=svirt_sandbox_file_t selevel=s0 recurse=true
                 - name: Write docker-puppet.py
                   copy: src=docker_puppet_script.yaml dest=/var/lib/docker-puppet/docker-puppet.py force=yes mode=0600
-{%- for role in roles %}
-                - include: {{role.name}}/host_prep_tasks.yaml
-                  when: tripleo_role_name == '{{role.name}}'
-{%- endfor %}
+                - import_tasks: {{role.name}}/host_prep_tasks.yaml
               tags:
                 - overcloud
                 - host_prep_steps
+{%- endfor %}
 
 {%- for step in range(1,deploy_steps_max) %}