Merge pull request #2643 from brauner/2018-09-23/cgroup_scoping_fixes

cgroups: implement monitor cgroup deletion

diff --cc src/lxc/cgroups/cgfsng.c
Simple merge

diff --cc src/lxc/cgroups/cgroup.c
Simple merge

diff --cc src/lxc/start.c
Simple merge

diff --cc src/lxc/start.h
Simple merge