Don't configure the replicaset on jenkins worker images.

util/packer/jenkins_worker.json

@@ -58,7 +58,7 @@
     "command": ". {{user `venv_dir`}}/bin/activate && ansible-playbook",
     "inventory_groups": "jenkins_worker",
     "extra_arguments": [
-      "-e \"jenkins_edx_platform_version={{user `test_platform_version`}} NEWRELIC_LICENSE_KEY={{user `new_relic_key`}} initialize_replica_set=false jenkins_worker_key_url='{{env `JENKINS_WORKER_KEY_URL`}}'\"",
+      "-e \"jenkins_edx_platform_version={{user `test_platform_version`}} NEWRELIC_LICENSE_KEY={{user `new_relic_key`}} initialize_replica_set=false mongo_configure_replica_set=false jenkins_worker_key_url='{{env `JENKINS_WORKER_KEY_URL`}}'\"",
       "-vvv"
       ]
   }, {