Comment 4 for bug 1397130

(gdb) bt
#0 0x00007f9fd650ad27 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1 0x00007f9fd650c418 in __GI_abort () at abort.c:89
#2 0x00007f9fd448f538 in cgmanager_get_pid_cgroup_sync () from /lib/x86_64-linux-gnu/libcgmanager.so.0
#3 0x00007f9fd6b2302b in cgm_controller_exists (controller=0x7f9fd6ca766b "name=systemd") at /build/buildd/libvirt-1.2.8/./src/util/cgmanager.c:296
#4 0x00007f9fd6b1aa3b in cg_get_cgroups (group=<optimized out>) at /build/buildd/libvirt-1.2.8/./src/util/vircgroup.c:374
#5 virCgroupDetectMounts (group=0x12f) at /build/buildd/libvirt-1.2.8/./src/util/vircgroup.c:412
#6 0x00007f9fd6b1bc53 in virCgroupDetect (parent=<optimized out>, path=<optimized out>, controllers=<optimized out>, pid=<optimized out>,
    group=<optimized out>) at /build/buildd/libvirt-1.2.8/./src/util/vircgroup.c:729
#7 virCgroupNew (pid=303, path=0x7f9fd6cf4dd8 "", parent=0x0, controllers=-1, group=0x7f9fbcff9700)
    at /build/buildd/libvirt-1.2.8/./src/util/vircgroup.c:1263
#8 0x00007f9fd6b1bec7 in virCgroupNewDetectMachine (name=0x7f9fc0279100 "instance-000015f8", drivername=0x7f9fc70c8ffb "qemu", pid=303,
    partition=0x7f9fc026c1a0 "/machine", controllers=-1124100352, group=0x7f9fc027cb50) at /build/buildd/libvirt-1.2.8/./src/util/vircgroup.c:1782
#9 0x00007f9fc7048ec5 in qemuConnectCgroup (driver=<optimized out>, vm=0x7f9fc027e080) at /build/buildd/libvirt-1.2.8/./src/qemu/qemu_cgroup.c:781
#10 0x00007f9fc705d447 in qemuProcessReconnect (opaque=0x12f, opaque@entry=0x7f9fc031b890) at /build/buildd/libvirt-1.2.8/./src/qemu/qemu_process.c:3322
#11 0x00007f9fd6b6c94e in virThreadHelper (data=<optimized out>) at /build/buildd/libvirt-1.2.8/./src/util/virthread.c:197
#12 0x00007f9fd68a10a5 in start_thread (arg=0x7f9fbcff9700) at pthread_create.c:309
#13 0x00007f9fd65ce84d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111