prepull: set async to 0 so that task wouldn't block others

roles/openshift_control_plane/tasks/main.yml

@@ -23,7 +23,7 @@
   when: control_plane_image.stdout_lines == []
   # 10 minutes to pull the image
   async: 600
-  poll: 10
+  poll: 0
   register: image_prepull
 
 - name: Open up firewall ports

roles/openshift_node/tasks/config.yml

@@ -12,7 +12,7 @@
   when: node_image.stdout_lines == []
   # 10 minutes to pull the image
   async: 600
-  poll: 10
+  poll: 0
   register: image_prepull
 
 - name: Install the systemd units