If we already triggered another exception, don't overwrite it with a
protection exception.

Only applies to old KVM instances without the virtual memory access
IOCTL in KVM.

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180409113019.14568-2-david@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>