cgroups: fix cgroup subsystem mounting

Originally, we aborted all of the cgroup setup if /sys/fs/cgroup/openrc
was already mounted. This  caused an issue in lxc containers, so we
should always allow the subsystems to be mounted.

X-Gentoo-Bug: 520606
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=520606

init.d/sysfs.in

@@ -100,14 +100,15 @@ mount_misc()
 mount_cgroups()
 {
 	mountinfo -q /sys/fs/cgroup || return 0
-	mountinfo -q /sys/fs/cgroup/openrc || return 0
 
+	if ! mountinfo -q /sys/fs/cgroup/openrc; then
 		local agent="@LIBEXECDIR@/sh/cgroup-release-agent.sh"
 		mkdir /sys/fs/cgroup/openrc
 		mount -n -t cgroup \
 			-o none,${sysfs_opts},name=openrc,release_agent="$agent" \
 			openrc /sys/fs/cgroup/openrc
 		echo 1 > /sys/fs/cgroup/openrc/notify_on_release
+	fi
 
 	yesno ${rc_controller_cgroups:-YES} && [ -e /proc/cgroups ] || return 0
 	while read name hier groups enabled rest; do