fix conditional check for ssh key

playbooks/roles/jenkins_worker/defaults/main.yml

@@ -15,5 +15,3 @@ jenkins_debian_pkgs:
 
 # packer direct download URL
 packer_url: "https://releases.hashicorp.com/packer/0.8.6/packer_0.8.6_linux_amd64.zip"
-
-jenkins_worker_key_url: null

playbooks/roles/jenkins_worker/tasks/system.yml

@@ -21,7 +21,7 @@
     user: "{{ jenkins_user }}"
     state: present
     key: "{{ jenkins_worker_key_url }}"
-  when: jenkins_worker_key_url
+  when: jenkins_worker_key_url is defined
   ignore_errors: yes
 
 - name: Set key permissions