nvme-loop: update tagset nr_hw_queues after reconnecting/resetting

We might have more/less queues once we reconnect/reset. For
example due to cpu going online/offline

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>