auditor recon dump is not consistent on new nodes

When you first bring up a node, and there's no data to audit the recon dump includes an empty disk:

ubuntu@saio:/etc/swift$ cat /var/cache/swift/node4/object.recon | python -m json.tool
{
    "object_auditor_stats_ALL": {},
    "object_auditor_stats_ZBF": {},
    "object_reconstruction_last": 1500319192.22745,
    "object_reconstruction_time": 0.00022380352020263673,
    "object_replication_last": 1500319107.354281,
    "object_replication_time": 9.981393814086914e-05,
    "replication_last": 1500319107.354281,
    "replication_stats": {
        "attempted": 0,
        "failure": 0,
        "hashmatch": 0,
        "remove": 0,
        "rsync": 0,
        "start": 1500319107.347603,
        "success": 0
    },
    "replication_time": 9.981393814086914e-05
}

Then if you run it *again* the keys are missing:

ubuntu@saio:/etc/swift$ cat /var/cache/swift/node4/object.recon | python -m json.tool
{
    "object_reconstruction_last": 1500319192.22745,
    "object_reconstruction_time": 0.00022380352020263673,
    "object_replication_last": 1500319107.354281,
    "object_replication_time": 9.981393814086914e-05,
    "replication_last": 1500319107.354281,
    "replication_stats": {
        "attempted": 0,
        "failure": 0,
        "hashmatch": 0,
        "remove": 0,
        "rsync": 0,
        "start": 1500319107.347603,
        "success": 0
    },
    "replication_time": 9.981393814086914e-05
}

Easiest way to observe is just running a single auditor on a brand new saio:

swift-init object-auditor once -nv -c 4

Then check the recon dump between passes, you can also set your run_pause to 0 and watch it toggle.

I think it would be better if once the auditor finished it wrote empty stats and the keys stayed there.