virtio: Fix ring size
virtio: Fix ring size

Fix error with tcp_test:
terminate called after throwing an instance of
'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::bad_any_cast> >'
  what():  boost::bad_any_cast: failed conversion using boost::any_cast

dwdm/scylla,slivne/seastar,justintung/scylla,acbellini/seastar,stamhe/scylla,cloudius-systems/seastar,leejir/seastar,justintung/scylla,dwdm/scylla,raphaelsc/scylla,bowlofstew/scylla,bowlofstew/scylla,scylladb/seastar,victorbriz/scylla,acbellini/scylla,cloudius-systems/seastar,victorbriz/scylla,duarten/scylla,shyamalschandra/seastar,raphaelsc/scylla,cloudius-systems/seastar,scylladb/scylla,wildinto/scylla,xtao/seastar,acbellini/seastar,ducthangho/imdb,scylladb/scylla,duarten/scylla,norcimo5/seastar,jonathanleang/seastar,linearregression/scylla,joerg84/seastar,raphaelsc/scylla,duarten/scylla,dwdm/seastar,asias/scylla,anzihenry/seastar,capturePointer/scylla,rluta/scylla,norcimo5/seastar,rluta/scylla,chunshengster/seastar,stamhe/seastar,scylladb/scylla,rentongzhang/scylla,victorbriz/scylla,mixja/seastar,sjperkins/seastar,flashbuckets/seastar,ducthangho/imdb,avikivity/seastar,wildinto/scylla,linearregression/scylla,avikivity/scylla,stamhe/scylla,slivne/seastar,linearregression/seastar,asias/scylla,dreamsxin/seastar,avikivity/seastar,scylladb/scylla,koolhazz/seastar,printedheart/seastar,shaunstanislaus/scylla,senseb/scylla,shyamalschandra/seastar,leejir/seastar,kangkot/scylla,jonathanleang/seastar,gwicke/scylla,scylladb/scylla-seastar,stamhe/seastar,kjniemi/scylla,glommer/scylla,bzero/seastar,wildinto/seastar,mixja/seastar,shaunstanislaus/scylla,linearregression/seastar,raphaelsc/seastar,syuu1228/seastar,raphaelsc/seastar,phonkee/scylla,bzero/seastar,kjniemi/seastar,justintung/scylla,aruanruan/scylla,slivne/seastar,norcimo5/seastar,anzihenry/seastar,scylladb/scylla-seastar,rentongzhang/scylla,acbellini/scylla,eklitzke/scylla,chunshengster/seastar,respu/scylla,shyamalschandra/seastar,wildinto/scylla,raphaelsc/seastar,flashbuckets/seastar,rentongzhang/scylla,capturePointer/scylla,aruanruan/scylla,scylladb/seastar,bowlofstew/seastar,gwicke/scylla,scylladb/seastar,dwdm/seastar,guiquanz/scylla,leejir/seastar,kjniemi/seastar,respu/scylla,bzero/seastar,avikivity/scylla,mixja/seastar,kjniemi/seastar,guiquanz/scylla,respu/scylla,aruanruan/scylla,stamhe/seastar,linearregression/seastar,shaunstanislaus/scylla,kangkot/scylla,sjperkins/seastar,senseb/scylla,asias/scylla,printedheart/seastar,sjperkins/seastar,capturePointer/scylla,wildinto/seastar,scylladb/scylla-seastar,dreamsxin/seastar,joerg84/seastar,tempbottle/scylla,avikivity/seastar,glommer/scylla,stamhe/scylla,tempbottle/seastar,kjniemi/scylla,dwdm/scylla,acbellini/seastar,jonathanleang/seastar,eklitzke/scylla,xtao/seastar,bowlofstew/scylla,tempbottle/seastar,wildinto/seastar,guiquanz/scylla,rluta/scylla,avikivity/scylla,syuu1228/seastar,bowlofstew/seastar,gwicke/scylla,hongliangzhao/seastar,acbellini/scylla,joerg84/seastar,syuu1228/seastar,kangkot/scylla,glommer/scylla,bowlofstew/seastar,tempbottle/seastar,flashbuckets/seastar,koolhazz/seastar,anzihenry/seastar,ducthangho/imdb,eklitzke/scylla,linearregression/scylla,tempbottle/scylla,dreamsxin/seastar,printedheart/seastar,senseb/scylla,hongliangzhao/seastar,phonkee/scylla,xtao/seastar,hongliangzhao/seastar,kjniemi/scylla,dwdm/seastar,chunshengster/seastar,phonkee/scylla,koolhazz/seastar,tempbottle/scylla