vhost: check better if `GET_VRING_BASE` message should reset the vring

We recently merged https://github.com/rust-vmm/vhost/pull/154 but we still need to figure out if we should reset the vring or not when `GET_VRING_BASE` message is handled.

@germag [mentioned](https://github.com/rust-vmm/vhost/pull/154#issuecomment-1538098518) that neither QEMU's libvhost-user nor DPDK does this, but they only disable vring.