fixes issue #28: CGroup properties not set.
Whenever scheduler finds matching rule for scheduled process, it calls
CGroup.get_group(name) to check if cgroup does exist. This used to check
only if cgroup is contained in the internal _CGroup_Cache - not if it really
does exist in cgroup filesystem.
So if the cgroup was removed outside ulatencyd and therefore was not
removed from _CGroup_Cache, cgroup will not be recreated and will loose
all settings (default parameters, rule parameters, parameters adjusted
+ CGroup.get_group(): test if cgroup is really present in filesystem,
otherwise return false or nil.
+ CGroup.new(): always create requested cgroup. If it is already
contained in _CGroup_Cache, replace it with new one. Code should check
its existence before calling CGroup.new() anyway.
Real fix would involve changing ulatencyd_cleanup.lua in a way it tells
ulatencyd to remove that cgroup. Ulatencyd should also update its internal
structures and do clean up, i.e. handle remaining memory charges.