config: enable kcounter cgroup subsys by default

Kcounter cgroup subsys is used to control resource usage of a cgroup by
enforcing an upper bound of resource counters. This is now required by AliIaaS
infrastructure to limit the tasks one cgroup can own.

Signed-off-by: Wenzhang <wenzhang.zzy@alibaba-inc.com>
Merge pull request #65 from danielzhou82/ai-kcounter

config: enable kcounter cgroup subsys by default