Cluster status reporting "Module 'pg_autoscaler' has failed: 'op'" in RHCS 4.x

Issue

• ceph cluster status is in HEALTH_ERR with below error

  # ceph -s
  cluster:
    id:     7f8b3389-5759-4798-8cd8-6fad4a9760a1
    health: HEALTH_ERR
          Module 'pg_autoscaler' has failed: 'op'
          too few PGs per OSD (4 < min 30)
  
  services:
    mon: 3 daemons, quorum ceph71,ceph72,ceph70 (age 2d)
    mgr: ceph72(active, starting, since 4s), standbys: ceph71, ceph70
    osd: 12 osds: 11 up (since 2d), 11 in (since 2w)
  
  data:
    pools:   2 pools, 16 pgs
    objects: 0 objects, 0 B
    usage:   11 GiB used, 154 GiB / 165 GiB avail
    pgs:     16 active+clean