When running with LXC 2.1+, ensure that our boxes have up-to-date config
keys by running the `lxc-update-config` utility that ships with LXC
2.1+.
When the command doesn't exist (LXC <2.1), we do nothing.
ref #445
`lxc-info -iH` to retrieve IP address was not available in early LXC
development but was there at LXC 1.0. Because we've bumped our minimum
LXC requirement to v1.0 recently, we can simplify the IP retrieval
process and also get rid of the `dnsmasq` fallback.
The previously hardcoded lxc path prevented the sudo wrapper from
working in environment with alternative `lxcpath`.
I had to move `sudo_wrapper` from `provider` to `LXC` because the
concept of "provider" is tied to a machine when a command sush as
`sudoers` is not.
Fixes#413 and #399
Previously, we hardcoded to using the ruby binary in /opt/vagrant[..].
On some systems, this path is incorrect, so instead we use the
path of the interpreter that is executing the `vagrant lxc sudoers`
command.
I ran into an issue locally where I didnt have lxc installed and some
commands were giving me back some false positives. Weird but this fixes
the problem I was facing.
