Description of problem:
MGR: The osd_memory_target_autotune option is not working as expected

- set osd_memory_target_autotune = true to enable and we should see the autotune start when this option is enabled.
- but in the workload-dfg RHCS 5 cluster, we are not seeing it happen.

What we see right now:

- The osd_memory_target_autotune enabled for all the 192 OSDs. Listing for one of them - 

- We did dump osd_memory_target value `config show` for all 192 OSDs and they still have the default value as 4G. 


# ceph tell osd.1 config show | grep osd_memory_target
    "osd_memory_target": "4294967296",
    "osd_memory_target_autotune": "true",
    "osd_memory_target_cgroup_limit_ratio": "0.800000",

- We went ahead and ran `ceph orch ps --daemon-type osd --format json-pretty` 

  {
    "container_id": "fedc4933cd26",
    "container_image_digests": [
      "registry.redhat.io/rhceph/rhceph-5-rhel8@sha256:55cb1de88341300daa1ab6d59e4897edc733
a3f90162149c21f18abe49ed87c7"
    ],
    "container_image_id": "2142b60d797408c7a0e9210489bd599cd7addb2d4c6e31da769eba248208ca44
",
    "container_image_name": "registry.redhat.io/rhceph/rhceph-5-rhel8@sha256:55cb1de8834130
0daa1ab6d59e4897edc733a3f90162149c21f18abe49ed87c7",
    "created": "2021-09-04T12:31:42.062065Z",
    "daemon_id": "1",
    "daemon_type": "osd",
    "hostname": "f23-h05-000-6048r.rdu2.scalelab.redhat.com",
    "is_active": false,
    "last_refresh": "2021-09-13T16:40:43.590086Z",
    "memory_usage": 9093519507,
    "osdspec_affinity": "defaultDG",
    "ports": [],
    "started": "2021-09-04T12:31:49.409595Z",
    "status": 1,
    "status_desc": "running",
    "version": "16.2.0-117.el8cp"
  },

- We did run the top command to see what is the exact usage at the system for this particular OSD


    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
 576023 ceph      20   0 6609044   3.9g  15824 S   5.6   1.5 449:20.13 /usr/bin/ceph-osd -n osd.1 -f --setuser ceph --setgroup ceph --default-log-to-file=false --defau+

Looks like the current set `osd_memory_target` is limiting it to the default value 4G but in `ceph orch` command we can clearly see the usage is listed around 9G.

"memory_usage": 9093519507


We will attach all the commands dumps!


Version-Release number of selected component (if applicable):
RHCS 5 - 16.2.0-117.el8cp

How reproducible:
Always