api for generating the list of variables of given controller

api for generating the list of variables of given controller

api for generating the list of variables of given controller:
changelog - v2:
fixed the space on the end of lines

  * int cgroup_get_value_name_count(struct cgroup_controller,  *controller)
  functions return the number of variables in "controller"

  * char *cgroup_get_value_name(struct cgroup_controller *controller, int index)
  function return the "index" variable of "controller"

Signed-off-by: Ivana Hutarova Varekova <varekova@redhat.com>
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>