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

@@ -348,9 +348,10 @@ outputs:
               tags:
                 - overcloud
                 - pre_deploy_steps
+{%- for role in roles %}
 
-            - hosts: {{primary_role_name}}:DEPLOY_TARGET_HOST
-              name: Host prep steps
+            - hosts: {{role.name}}
+              name: {{role.name}} Host prep steps
               gather_facts: {{ '"{{' }} gather_facts | default(false) {{ '}}"' }}
               any_errors_fatal: yes
               vars:
@@ -365,13 +366,11 @@ outputs:
                 docker_puppet_process_count: DOCKER_PUPPET_PROCESS_COUNT
                 docker_puppet_mount_host_puppet: DOCKER_PUPPET_MOUNT_HOST_PUPPET
               tasks:
-{%- for role in roles %}
                 - import_tasks: {{role.name}}/host_prep_tasks.yaml
-                  when: tripleo_role_name == '{{role.name}}'
-{%- endfor %}
               tags:
                 - overcloud
                 - host_prep_steps
+{%- endfor %}
 
 {%- for step in range(1,deploy_steps_max) %}