KVM: VMX: Fix locking imbalance on emulation failure

We have to disable preemption and IRQs on every exit from
handle_invalid_guest_state, otherwise we generate at least a
preempt_disable imbalance.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>