Fix warnings map to be thread-local
Fix warnings map to be thread-local

The map is mutated so it should be thread-local. This will make the
warnings printed once per core, but I guess it's not a big deal.

guiquanz/scylla,gwicke/scylla,phonkee/scylla,gwicke/scylla,rentongzhang/scylla,shaunstanislaus/scylla,wildinto/scylla,acbellini/scylla,victorbriz/scylla,phonkee/scylla,avikivity/scylla,aruanruan/scylla,justintung/scylla,scylladb/scylla,rluta/scylla,shaunstanislaus/scylla,guiquanz/scylla,gwicke/scylla,kjniemi/scylla,rentongzhang/scylla,capturePointer/scylla,guiquanz/scylla,aruanruan/scylla,wildinto/scylla,avikivity/scylla,glommer/scylla,victorbriz/scylla,dwdm/scylla,victorbriz/scylla,tempbottle/scylla,duarten/scylla,duarten/scylla,aruanruan/scylla,eklitzke/scylla,stamhe/scylla,rentongzhang/scylla,kangkot/scylla,linearregression/scylla,asias/scylla,tempbottle/scylla,raphaelsc/scylla,acbellini/scylla,asias/scylla,scylladb/scylla,scylladb/scylla,raphaelsc/scylla,senseb/scylla,avikivity/scylla,stamhe/scylla,phonkee/scylla,wildinto/scylla,respu/scylla,capturePointer/scylla,respu/scylla,justintung/scylla,respu/scylla,shaunstanislaus/scylla,rluta/scylla,kjniemi/scylla,bowlofstew/scylla,stamhe/scylla,glommer/scylla,capturePointer/scylla,linearregression/scylla,dwdm/scylla,linearregression/scylla,duarten/scylla,kangkot/scylla,bowlofstew/scylla,acbellini/scylla,glommer/scylla,eklitzke/scylla,raphaelsc/scylla,senseb/scylla,eklitzke/scylla,justintung/scylla,dwdm/scylla,rluta/scylla,senseb/scylla,asias/scylla,scylladb/scylla,tempbottle/scylla,kjniemi/scylla,kangkot/scylla,bowlofstew/scylla