vhost: Prepare v0.15.0 release

[ShadowCurse]

Summary of the PR

Prepare v0.15.0 release

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[stefano-garzarella]

Should we include also #328 ?

[ShadowCurse]

So I looked at #328, but for it to work, we need updated virtio-queue (rust-vmm/vm-virtio#368) and that is blocked by the kani proofs.

[stefano-garzarella]

@ShadowCurse right, but we should be near to fix it: rust-vmm/vm-virtio#371

[stefano-garzarella]

Or we should disable kani

[ShadowCurse]

Ok, let's wait for the fix.