Log on boot errors with one role

We didn't log boot errors if there was one role because there was no
barrier and the logging is done by the first host to close the barrier.

Let's always create the barrier to fix this.

test/integration/broken_deploy_test.rb

@@ -26,7 +26,7 @@ class BrokenDeployTest < IntegrationTest
   private
     def assert_failed_deploy(output)
       assert_match "Waiting for the first healthy web container before booting workers on vm3...", output
-      assert_match /First web container is unhealthy on vm[12], not booting other roles/, output
+      assert_match /First web container is unhealthy on vm[12], not booting any other roles/, output
       assert_match "First web container is unhealthy, not booting workers on vm3", output
       assert_match "nginx: [emerg] unexpected end of file, expecting \";\" or \"}\" in /etc/nginx/conf.d/default.conf:2", output
       assert_match 'ERROR {"Status":"unhealthy","FailingStreak":0,"Log":[]}', output