virtio: de-futurize transmit
virtio: de-futurize transmit

Move completion handling (destroy packet, adjust descriptors count) to
a completion function rather than a future.  Reduces allocations and task
executed.

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