Added -M option to lssubsys to show multiple mount points of hierarchies.

Added -M option to lssubsys to show multiple mount points of hierarchies.

Now libcgroup is aware of hierarchies and all its mount points, let's
extend lssubsys to show them. The patch also renames few variables to be
descriptive, 'name' is not name of controller, it's list of controllers.

Now (and also with the patch, '-m' works the same):
$ lssubsys -m
cpuset,cpuacct /cgroup/cpu
memory /cgroup/memory

With the patch:
$ lssubsys -M
cpuset,cpuacct /cgroup/cpu
cpuset,cpuacct /cgroup/cpu2
memory /cgroup/memory

Signed-off-by: Jan Safranek <jsafrane@redhat.com>
Acked-by: Ivana Hutarova Varekova<varekova@redhat.com>