notify slowing down cloud-hypervisor boot

[yorickvP]

When I set microvm.vsock.cid = 4; hypervisor = "cloud-hypervisor"; and run my microvm as a systemd unit, the VM takes about 30 seconds to boot. When I run it without the cid, it takes 6 seconds to boot.

[SuperSandro2000]

You are sure this is not just a dupe of #366 ? I have also observed that boot time seems to scale badly with image size and there is an upstream issue about bad scaling block device performance and a PR to fix that.