cgroups: requires initialization after the "setup" stage

The cgroups module requires busybox and shutil to properly initialise.
This patch required the module to be initialized once the setup has
completed.

Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
diff --git a/devlib/module/cgroups.py b/devlib/module/cgroups.py
index 942ed2c..c754914 100644
--- a/devlib/module/cgroups.py
+++ b/devlib/module/cgroups.py
@@ -231,6 +231,7 @@
 class CgroupsModule(Module):
 
     name = 'cgroups'
+    stage = 'setup'
     cgroup_root = '/sys/fs/cgroup'
 
     @staticmethod