cgfsng: cgfsng_monitor_enter()

cgfsng: cgfsng_monitor_enter()

brauner@wittgenstein|~
> sudo systemctl status lxc@c1
● lxc@c1.service - LXC Container: c1
   Loaded: loaded (/lib/systemd/system/lxc@.service; disabled; vendor preset: enabled)
   Active: active (running) since Tue 2018-09-11 10:42:22 CEST; 38s ago
     Docs: man:lxc-start
           man:lxc
  Process: 29855 ExecStart=/usr/bin/lxc-start -n c1 -p /run/lxc/c1.pid (code=exited, status=0/SUCCESS)
    Tasks: 18 (limit: 4915)
   Memory: 32.1M
   CGroup: /system.slice/system-lxc.slice/lxc@c1.service
           ├─lxc.monitor
           │ └─c1
           │   └─29870 [lxc monitor] /var/lib/lxc c1
           └─lxc.payload
             └─c1
               ├─init.scope
               │ └─29878 /sbin/init
               └─system.slice
                 ├─console-getty.service
                 │ └─30028 /sbin/agetty -o -p -- \u --noclear --keep-baud console 115200,38400,9600 linux
                 ├─cron.service
                 │ └─30019 /usr/sbin/cron -f
                 ├─dbus.service
                 │ └─30020 /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only
                 ├─networkd-dispatcher.service
                 │ └─30016 /usr/bin/python3 /usr/bin/networkd-dispatcher --run-startup-triggers
                 ├─rsyslog.service
                 │ └─30017 /usr/sbin/rsyslogd -n
                 ├─system-container\x2dgetty.slice
                 │ ├─container-getty@0.service
                 │ │ └─30027 /sbin/agetty -o -p -- \u --noclear --keep-baud pts/0 115200,38400,9600 vt220
                 │ ├─container-getty@1.service
                 │ │ └─30030 /sbin/agetty -o -p -- \u --noclear --keep-baud pts/1 115200,38400,9600 vt220
                 │ ├─container-getty@2.service
                 │ │ └─30026 /sbin/agetty -o -p -- \u --noclear --keep-baud pts/2 115200,38400,9600 vt220
                 │ └─container-getty@3.service
                 │   └─30029 /sbin/agetty -o -p -- \u --noclear --keep-baud pts/3 115200,38400,9600 vt220
                 ├─systemd-journald.service
                 │ └─29976 /lib/systemd/systemd-journald
                 ├─systemd-logind.service
                 │ └─30018 /lib/systemd/systemd-logind
                 ├─systemd-networkd.service
                 │ └─29996 /lib/systemd/systemd-networkd
                 ├─systemd-resolved.service
                 │ └─30014 /lib/systemd/systemd-resolved
                 └─systemd-udevd.service
                   └─29986 /lib/systemd/systemd-udevd

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>