core: make future::rescue() return a future<>
core: make future::rescue() return a future<>

This will allow to compose rescue() just like then().

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