API: Return 0 for key and counter cache's metrics
API: Return 0 for key and counter cache's metrics

Until we'll support key and counter cache, it is reasonable to return 0
for their statistic and sizes.

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@cloudius-systems.com>

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