Simplify cloud-init check and use command

As per the discussion here:
https://review.opendev.org/c/openstack/tripleo-ansible/+/840509/comments/44ba7337_6f80dbd7

This change simplifies the check for cloud-init and changes from shell
to command.

Change-Id: I48dcdc9d6cef6e7dd5d9a8dd0e0b733531f3d302

common/deploy-steps-tasks-step-0.yaml

@@ -13,7 +13,7 @@
   become: true
   register: cloud_init_enabled
 - name: Check if cloud-init is disabled via kernel args
-  shell: cat /proc/cmdline | grep -q cloud-init=disabled
+  command: grep -q cloud-init=disabled /proc/cmdline
   failed_when: false
   check_mode: false
   register: cloud_init_vendor_disabled