[UI] When changing configuration of an Interface, one has to enter the config twice

[webteam-app]

Bug originally filed by bladernr at https://bugs.launchpad.net/bugs/1840049

See the attached video.

If I have an interface that is configured, and I then change that configuration so it is put on a different fabric and subnet, when I click Save, instead of saving, MAAS changes the Interface to Unconfigured, forcing me to configure the interface a second time.

This is pretty easily and reliably reproducible on MAAS 2.6, I've had it happen on multiple systems when trying to move an interface from one Fabric to another.

This does not seem to occur when configuring one for the first time, or when simply changing the type of addressing (e.g. from DHCP to AutoAssign). It only seems to happen when I change one from one Fabric to Another, and choose a different subnet.

MAAS version: 2.6.0 (7802-g59416a869-0ubuntu1~18.04.1)

[huwshimi]

Requires investigation on the API side.

[Caleb-Ellis]

This is a bug in the websocket API