cloud.lxc: autostart support

[kiorky]

This is the 1.0 version way of autostarting lxc containers.

[ghost]

Test Failed.

If the failures are unrelated to your code, don't stress, a core developer will know these apart.
In the future, if possible, please branch off a passing commit to avoid false positives.
Refer to this link for build results: http://jenkins.saltstack.com/job/salt-pr-build/3275/

[techhat]

Thanks @kiorky!