Firecracker doesn't close when running `halt` or `poweroff` in the guest

[serban300]

After running halt or poweroff in the guest the guest kernel halts, but the Firecracker process continues to run.

The problem is that we don't receive a KVM_EXIT_HLT signal from KVM. Seems related to this if statement in the kernel.

There might be a problem with the way we configure the lapic.

I Tested it on host 4.15 with guest 4.15 and host 5.5 with guest 5.5 and it reproduced in both cases.