Fix rootshared creating a new shared peer group

As soon as we change the root directory to be private the sharing is
disassociated and making it shared again will simply create a new, empty,
peer group.

Instead, simply make /sys private before mounting over it!

	the same feature will be supported through module options

Linux adds the loopback addresses to 'lo' automatically when it goes up, but you
have to up it to allow communication.

This is primarily required to support different DNS setups in the namespaces.

To use it create a directory for a user's netns in `/etc/netns/<user>`. Config
files placed directly underneath it will get bind mounted over files in `/etc`
upon entering the namespace as usual. See ip-netns(8).