Ceph Dashboard - installing Ceph Storage Dashboard for containerized Ceph fails with: ""The conditional check 'container_name' failed. The error was: error while evaluating conditional (container_name): Unable to look up a name ..."

Issue

• While deploying Red Hat Ceph Storage Dashboard for Containerized version of Red Hat Ceph Storage 3 the cephmetrics-ansible playbook fails with following error:

  TASK [ceph-mgr : Prefix the mgr command with a docker command] **********************************************************************************
  task path: /usr/share/cephmetrics-ansible/roles/ceph-mgr/tasks/main.yml:26
  fatal: [mons01]: FAILED! => {
    "msg": "The conditional check 'container_name' failed. The error was: error while evaluating conditional (container_name): Unable to look up a name or   access an attribute in template string ({% if ceph-mgr-mons01 %} True {% else %} False {% endif %}).\nMake sure your variable name does  not contain   invalid characters like '-': unsupported operand type(s) for -: 'StrictUndefined' and 'StrictUndefined'\n\nThe error appears to have been in '/usr/share/  cephmetrics-ansible/roles/ceph-mgr/tasks/main.yml': line 26, column 3, but may\nbe elsewhere in the file depending on the exact syntax problem.\n\nThe   offending line appears to be:\n\n\n- name: Prefix the mgr command with a docker command\n  ^ here\n"