API: column family stats break the map_reduce functionality
API: column family stats break the map_reduce functionality

This patch replaces the helper function for column family with two
function, one that collect the relevant column family from all shareds
and another one that do the translation to json object.

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

scylladb/scylla,kjniemi/scylla,kjniemi/scylla,kjniemi/scylla,scylladb/scylla,duarten/scylla,raphaelsc/scylla,avikivity/scylla,scylladb/scylla,raphaelsc/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,duarten/scylla,raphaelsc/scylla