Update container executor to use CGROUP2_SUPER_MAGIC in cgroup 2 scenarios

/**
 * Write the pid of the current process to the cgroup file.
 * cgroup_file: Path to cgroup file where pid needs to be written to.
 */
static int write_pid_to_cgroup_as_root(const char* cgroup_file, pid_t pid) {
  int rc = 0;
  uid_t user = geteuid();
  gid_t group = getegid();
  if (change_effective_user(0, 0) != 0) {
    rc =  -1;
    goto cleanup;
  }

  // statfs
  struct statfs buf;
  if (statfs(cgroup_file, &buf) == -1) {
    fprintf(LOGFILE, "Can't statfs file %s as node manager - %s\n", cgroup_file,
           strerror(errno));
    rc = -1;
    goto cleanup;
  } else if (buf.f_type != CGROUP_SUPER_MAGIC) {
    fprintf(LOGFILE, "Pid file %s is not located on cgroup filesystem\n", cgroup_file);
    rc = -1;
    goto cleanup;
  }