Systemd changes the cgroup of processes despite they configured with cgexec

Issue

• systemd changes the cgroup configured by cgexec

  $ cgexec -g memory:myapp.myapp myapp
  # cat /proc/3465959/cgroup
  12:memory:/myapp.myapp
  11:devices:/system.slice/gdm.service
  10:pids:/user.slice/user-1932628993.slice/session-2062.scope
  9:blkio:/system.slice/gdm.service
  8:perf_event:/
  7:freezer:/
  6:net_cls,net_prio:/
  5:cpu,cpuacct:/
  4:cpuset:/
  3:hugetlb:/
  2:rdma:/
  1:name=systemd:/user.slice/user-1932628993.slice/session-2062.scope 
  
  (After some minutes)
  
  # cat /proc/3465959/cgroup
  12:memory:/user.slice/user-1932628993.slice/session-2062.scope
  11:devices:/
  10:pids:/user.slice/user-1932628993.slice/session-2062.scope
  9:blkio:/
  8:perf_event:/
  7:freezer:/
  6:net_cls,net_prio:/
  5:cpu,cpuacct:/
  4:cpuset:/
  3:hugetlb:/
  2:rdma:/
  1:name=systemd:/user.slice/user-1932628993.slice/session-2062.scope