libcgrouptest: rename get_controller() to is_subsystem_enabled()

libcgrouptest: rename get_controller() to is_subsystem_enabled()

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

This patch renames the function get_controllers() to a more
meaningful name is_subsystem_enabled().

history:
The code in the patch is part of a patch sent in an earlier patchset,
which somehow got dropped (looks an older version of that patch was
merged to the tree). Adding this patch makes everything upstream upto
the discussion held on the list.

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@314 4f4bb910-9a46-0410-90c8-c897d4f1cd53