Changelog v2:

Changelog v2:
 * Use clock_gettime(2) for getting timestamp since a system boot.
 * Change parent_info's memory to dynamic allocation.

This patch is for changing the cgroup of a forked process while parent
changing.

This patch adds the following sequence:
 1. Store both the timestamp and the process-id when changing the cgroup.
 2. If receiving a PROC_EVENT_FORK packet, check its parent-pid and its
    timestamp.
 3. If its parent-pid and the stored process-id are same and its timestamp
    is older than the stored timestamp, change the cgroup of forked process.

Thanks
Ken'ichi Ohmichi

Signed-off-by: Ken'ichi Ohmichi <oomichi@mxs.nes.nec.co.jp>
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>