libcgrouptest:attach exclusive pid support in test_cgroup_attach_task() function

libcgrouptest:attach exclusive pid support in test_cgroup_attach_task() function

From: Sudhir Kumar <skumar@linux.vnet.ibm.com>

The function test_attach_task_pid() was attaching the process calling the
function to a group and did not have support to take any pid for attaching
it to a group. This patch does that.

Signed-off-by: Sudhir Kumar <skumar@linux.vnet.ibm.com>
Acked-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
git-svn-id: https://libcg.svn.sourceforge.net/svnroot/libcg/trunk@310 4f4bb910-9a46-0410-90c8-c897d4f1cd53