keyspace: use emplace instead of the [] operator
keyspace: use emplace instead of the [] operator

It inflicted a lot of pain recently. Avoid it.

Signed-off-by: Glauber Costa <f8b79557d19b40666ebe336545a0b6178af65685@cloudius-systems.com>

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