mutation_partition: support reading rows in reversed order
mutation_partition: support reading rows in reversed order

Signed-off-by: Paweł Dziepak <e29bb3265626c60caf76d587cabdfcd8b379ef80@cloudius-systems.com>

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