Backport - stable/icehouse - Creates a lxc-system-manage script for common operational tasks.

This creates a simple to use lxc-system-manage script that allows
the user to interact with some of the LXC internals that may need
to be adjusted and or recreated.

Cherry-pick from: f640f51
Related issue: https://github.com/rcbops/ansible-lxc-rpc/issues/434