Skip upgrade steps where no tasks are defined

Use heat conditions to skip resources (conditionally create them)
when there are no tasks to deploy.

This requires the heat fix Iefae1fcea720bee4ed69ad1a5fe403d52d54433c

Partially-Implements: blueprint overcloud-upgrades-per-service
Change-Id: I2f43fb922d122ffade20e35738f0ba3bb56a4492

puppet/major_upgrade_steps.j2.yaml

@@ -16,6 +16,23 @@ parameters:
       Setting to a previously unused value during stack-update will trigger
       the Upgrade resources to re-run on all roles.
 
+conditions:
+  # Conditions to disable any steps where the task list is empty
+{% for step in range(0, upgrade_steps_max) %}
+  {% for role in roles %}
+  UpgradeBatchConfig_Step{{step}}Enabled:
+    not:
+      equals:
+        - {get_param: [role_data, {{role.name}}, upgrade_batch_tasks]}
+        - []
+  UpgradeConfig_Step{{step}}Enabled:
+    not:
+      equals:
+        - {get_param: [role_data, {{role.name}}, upgrade_tasks]}
+        - []
+  {% endfor %}
+{% endfor %}
+
 resources:
 
 # Upgrade Steps for all roles, batched updates
@@ -25,6 +42,7 @@ resources:
   # Step {{step}} resources
   {{role.name}}UpgradeBatchConfig_Step{{step}}:
     type: OS::TripleO::UpgradeConfig
+    condition: UpgradeBatchConfig_Step{{step}}Enabled
   # The UpgradeConfig resources could actually be created without
   # serialization, but the event output is easier to follow if we
   # do, and there should be minimal performance hit (creating the
@@ -41,6 +59,7 @@ resources:
 
   {{role.name}}UpgradeBatch_Step{{step}}:
     type: OS::Heat::StructuredDeploymentGroup
+    condition: UpgradeBatchConfig_Step{{step}}Enabled
   {% if step > 0 %}
     depends_on:
       {% for dep in roles %}
@@ -69,6 +88,7 @@ resources:
   # Step {{step}} resources
   {{role.name}}UpgradeConfig_Step{{step}}:
     type: OS::TripleO::UpgradeConfig
+    condition: UpgradeConfig_Step{{step}}Enabled
   # The UpgradeConfig resources could actually be created without
   # serialization, but the event output is easier to follow if we
   # do, and there should be minimal performance hit (creating the
@@ -91,6 +111,7 @@ resources:
   {% if not role.disable_upgrade_deployment|default(false) %}
   {{role.name}}Upgrade_Step{{step}}:
     type: OS::Heat::StructuredDeploymentGroup
+    condition: UpgradeConfig_Step{{step}}Enabled
     depends_on:
   {% if step > 0 %}
       {% for dep in roles %}