build: fix default for tristate configs
build: fix default for tristate configs

Should be None, not False, so that notes are emitted if an optional package is
not installed.

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