[CEPH-83575880]Automation of user modify with --placement-id

[ckulal]

[CEPH-83575880]Automation of user modify with --placement-id

radosgw-admin user modify --uid --placement-id should not cause any crash BZ: https://bugzilla.redhat.com/show_bug.cgi?id=2228157

Logs: http://magna002.ceph.redhat.com/ceph-qe-logs/Chaithra/ceph83575880/

Pass-log for existing script where exec_shell_command method in use: https://github.com/red-hat-storage/ceph-qe-scripts/blob/master/rgw/v2/tests/s3_swift/test_bucket_listing.py#L85 http://magna002.ceph.redhat.com/ceph-qe-logs/Chaithra/ceph83575880/test_bucket_list_not_truncated.console.log

https://github.com/red-hat-storage/ceph-qe-scripts/blob/master/rgw/v2/tests/s3_swift/test_Mbuckets_with_Nobjects.py#L611 http://magna002.ceph.redhat.com/ceph-qe-logs/Chaithra/ceph83575880/test_datalog_trim_command.console.log

[openshift-ci[bot]]

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