Most notable changes are about mounting cgroups inside container.

Changes(from docker/libcontainer v2.2.1 https://github.com/docker/libcontainer/releases/tag/v2.2.1):
* Fix handling name= cgroups
* Tests for mounting cgroups
* Substract bindmount path from cgroup dir
* Add cgroup mount in the recommended config
* Correct tmpfs mount for cgroup
* Fix error when memory cgroup not mounted
* the data type should be int8 for ppc64le
* Remove deserialization tests.
* Add oom-kill-disable support for systemd
* Fixing test step for memory swappiness
* Remove sample configs from libcontainer
* Rename SystemProperties to Sysctl and make it available in the runc config
* Treat -1 as default value for memory swappiness.
* Remove apparmor profile generation from libcontainer
* Fix build tags
* libcontainer: user: update tests for GetAdditionalGroups
* libcontainer: user: fix GetAdditionalGroupsPath to match API
* Windows: Factor out seccomp
* checkpoint/restore commands support 'file-locks' option.
* Windows: Factor out CloseExecFrom
* Allow hyphen in "id" (based on `cwd` pathname)
* libcontainer: gofmt pass
* Fix panic in seccomp test on error
* Remove nsinit from libcontainer README.md