Add LXD radio option to Add KVM form.

[Caleb-Ellis]

Done

• Added LXD radio option to Add KVM form, so you can choose between virsh and LXD.
• Driveby - remove ability to select more than one storage pool when composing machines from LXD pod.
• Driveby - increase delay when hackily updating pod machine list with newly composed machine. When testing composing machines from a LXD pod it wouldn't show up sometimes

QA

• Go to /kvm and select Add KVM from the top right
• Check that the form matches the design, noting that the copy will be added later.
• Go to /rsd and check that the form there remains as before.
• Go to the bolla lxd pod and compose machine
• Check that you can only choose one storage pool.
• Compose a machine and check that the pod machine list updates correctly.

Fixes

Fixes canonical-web-and-design/MAAS-squad#1918
Fixes #1017

Screenshot

[Caleb-Ellis]

@lilyvidenova I've added UX needed just to check if the copy for the help text is still not ready, so we'll add it in a follow up later on?

[Caleb-Ellis]

Adding UX + 1 to confirm copy is to come later