tools/ceph_objectstore_tool: Add duplicate pg log entries injection

tools/ceph_objectstore_tool: Add duplicate pg log entries injection

To be able to recreate and test pg log duplicate entries, a new option
added to the COT: --op pg-log-inject-dups we will also need to provide
--file json_arry of dups, it can get as many dups that need to be inject

the json for dups is in the following format:
{"reqid": "client.n.n:n", "version": "n'n", "user_version": n, "return_code": n}

Signed-off-by: Nitzan Mordechai <nmordec@redhat.com>