Currently, we mark an IO request to STATE_IOREQ_READY state before
IO handlers in xen HV, i.e. vmx_portio_intercept or vmx_mmio_intercept.
Actually, STATE_IOREQ_READY means it's ready for DM handling, only if IO
handlers in xen HV won't handle it, it should be passed to DM. This
fixes this issue.