adapt to optional cc.failed_jobs parameter and add unit test

jobs/cloud_controller_clock/spec

@@ -116,7 +116,6 @@ properties:
 
   cc.failed_jobs.max_number_of_failed_delayed_jobs:
     description: "Maximum number of failed jobs that should stay in cloud controller database before being cleaned up"
-    default: 100000
 
   cc.pending_droplets.frequency_in_seconds:
     description: "How often the pending droplets cleanup job runs"

jobs/cloud_controller_clock/templates/cloud_controller_ng.yml.erb

@@ -85,7 +85,9 @@ audit_events:
 
 failed_jobs:
   cutoff_age_in_days: <%= p("cc.failed_jobs.cutoff_age_in_days") %>
-  max_number_of_failed_delayed_jobs: <%= p("cc.failed_jobs.max_number_of_failed_delayed_jobs") %>
+  <% if_p("cc.failed_jobs.max_number_of_failed_delayed_jobs") do |max_number_of_failed_delayed_jobs| %>
+  max_number_of_failed_delayed_jobs: <%= max_number_of_failed_delayed_jobs %>
+  <% end %>
   frequency_in_seconds: <%= p("cc.failed_jobs.frequency_in_seconds") %>
 
 completed_tasks:

spec/cloud_controller_ng/cloud_controller_ng_spec.rb

@@ -624,6 +624,23 @@ module Test
               end
             end
           end
+
+          describe  'max_number_of_failed_delayed_jobs' do
+            context "when 'cc.failed_jobs.max_number_of_failed_delayed_jobs' is set" do
+              it 'renders max_number_of_failed_delayed_jobs into the ccng config' do
+                merged_manifest_properties['cc'].store('renderer', { 'max_number_of_failed_delayed_jobs' => 1000 })
+                template_hash = YAML.safe_load(template.render(merged_manifest_properties, consumes: links))
+                expect(template_hash['failed_jobs']['max_number_of_failed_delayed_jobs']).to eq(1000)
+              end
+            end
+
+            context "when 'cc.failed_jobs.max_number_of_failed_delayed_jobs' is not set (default)" do
+              it 'does not render max_number_of_failed_delayed_jobs into the ccng config' do
+                template_hash = YAML.safe_load(template.render(merged_manifest_properties, consumes: links))
+                expect(template_hash['failed_jobs']).not_to have_key(:max_number_of_failed_delayed_jobs)
+              end
+            end
+          end
         end
       end
     end