core: add open_flags::exclusive (O_EXCL)
core: add open_flags::exclusive (O_EXCL)

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