kvmtool: correct order of the vcpu destructor

The vcpu module is a core component which should be removed last, but the
destructor was mistakenly marked as something that should be done first.

This would cause the vcpu data to be freed up before anything else had the
chance to exit, and assuming that that data was still valid - causing use
after frees.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>