Update libcontainer dec8

This updates the config with a namespace struct that allows any of the namespaces to be joined at the create of a container instead of one off fields for NET and IPC.  

This also adds support of cpuset.mems being implemented in #9536
Yeah, this is an issue. Probably for future we can make `type Namespaces []Namespace` with implemented operations, not sure how it will be in json though.