create directory for commitlog
create directory for commitlog

The same way we create a directory for the sstables, we should do it for the
commitlog.

If you, like me, have been using the --datadir directive, the fact that we
don't do it would have slipped away: when using --datadir, both the commitlog
and sstables will be put in this same root.

However, when using the system defaults from the configuration file, this won't
be true.

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

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