"auto assign" on unmanaged subnet used the gateway IP for the node

maas 1.9.0+bzr4533-0ubuntu1~trusty1

On a node with two nics, I chose an unmanaged subnet for the second nic and selected "auto assign". After deployment, that nic got the same IP as the subnet's gateway. See attached screenshot.

Here, with the node still deployed:
andreas@nsn7:~$ maas admin-atlas subnet statistics subnet-13 include_ranges=true
Success.
Machine-readable output follows:
{
    "total_addresses": 254,
    "usage_string": "0%",
    "num_available": 253,
    "ranges": [
        {
            "start": "10.96.130.1",
            "end": "10.96.130.1",
            "purpose": [
                "assigned-ip"
            ],
            "num_addresses": 1
        },
        {
            "start": "10.96.130.2",
            "end": "10.96.130.254",
            "purpose": [
                "unused"
            ],
            "num_addresses": 253
        }
    ],
    "largest_available": 253,
    "num_unavailable": 1,
    "usage": 0.003937007874015748,
    "inefficiency_string": "TBD",
    "available_string": "100%"
}

Same call with the node released:
andreas@nsn7:~$ maas admin-atlas subnet statistics subnet-13 include_ranges=true
Success.
Machine-readable output follows:
{
    "total_addresses": 254,
    "usage_string": "0%",
    "num_available": 254,
    "ranges": [
        {
            "start": "10.96.130.1",
            "end": "10.96.130.254",
            "purpose": [
                "unused"
            ],
            "num_addresses": 254
        }
    ],
    "largest_available": 254,
    "num_unavailable": 0,
    "usage": 0.0,
    "inefficiency_string": "TBD",
    "available_string": "100%"
}