Region controller fails to run commissioning scripts in proxied environment

Using exactly the same configuration 3.3.0 does not return any interfaces on a controller

3.3.0

$ maas root rack-controllers read|grep interface
        "interface_test_status": -1,
        "interface_test_status_name": "Unknown",
        "interface_set": [],

3.2.6

$ maas root rack-controllers read|grep interface
        "interface_set": [
                "interface_speed": 0,
                "resource_uri": "/MAAS/api/2.0/nodes/cekbha/interfaces/1/"
                "interface_speed": 0,
                "resource_uri": "/MAAS/api/2.0/nodes/cekbha/interfaces/2/"
                "interface_speed": 0,
                "resource_uri": "/MAAS/api/2.0/nodes/cekbha/interfaces/3/"
                "interface_speed": 0,
                "resource_uri": "/MAAS/api/2.0/nodes/cekbha/interfaces/4/"
                "interface_speed": 0,
                "resource_uri": "/MAAS/api/2.0/nodes/cekbha/interfaces/5/"
        "interface_test_status": -1,
        "interface_test_status_name": "Unknown",

just a sample

"interface_set": [
            {
                "enabled": true,
                "numa_node": 0,
                "id": 1,
                "links": [],
                "discovered": null,
                "tags": [],
                "parents": [],
                "firmware_version": null,
                "vendor": "Red Hat, Inc.",
                "link_connected": true,
                "name": "enp1s0",
                "params": "",
                "mac_address": "52:54:56:58:00:01",
                "interface_speed": 0,
                "system_id": "cekbha",
                "effective_mtu": 1500,
                "product": null,
                "vlan": {
                    "vid": 2741,
                    "mtu": 1500,
                    "dhcp_on": true,
                    "external_dhcp": null,
                    "relay_vlan": null,
                    "fabric": "default",
                    "secondary_rack": null,
                    "primary_rack": "cekbha",
                    "space": "oam-space",
                    "id": 5001,
                    "fabric_id": 2,
                    "name": "untagged",
                    "resource_uri": "/MAAS/api/2.0/vlans/5001/"
                },
                "children": [
                    "broam"
                ],
                "type": "physical",
                "sriov_max_vf": 0,
                "link_speed": 0,
                "resource_uri": "/MAAS/api/2.0/nodes/cekbha/interfaces/1/"

...

Logs and artifacts

https://oil-jenkins.canonical.com/artifacts/f61fd6b2-db2e-48fc-8166-85b31a2ce183/index.html