LXC bug fix

This fixes two bugs in the LXC module:

1) #7652, pertaining to a change from list to list_.

2) A bug in the handling of lxc profiles.

It also fixes the lxc nic/profile docs, and adds methods for getting and setting cgroup parameters.

@basepi you asked that I ping you about merging this to 0.17 since it contains bug fixes.