Set unattended-upgrades on Ubuntu hosts

[edunham]

Not sure if this is the best way, but http://blog.viraptor.info/post/75262988169/ubuntu-unattended-upgrades-the-salt-way suggests it.

Fixes #275

r? @aneeshusa

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This change is

[aneeshusa]

I don't think we actually need the cmd.wait here, the debconf.set should handle everything. We should check in Vagrant. Also FYI, cmd.wait has recently been deprecated, so we shouldn't use it in any new commits (I removed our last remaining uses during the Android refactor).

[aneeshusa]

We'll also need a pkg.installed state to install the unattended-upgrades package, which should require the debconf.set state (we can nest them under the same ID).

[aneeshusa]

Actually, I think we'll need to replace the cmd.wait state with a file.managed state that does the same thing by putting the following into /etc/apt/apt.conf.d/20auto-upgrades:

APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Unattended-Upgrade "1";

[aneeshusa]

Do we want the machines to auto-reboot if necessary? I'm assuming not, but if so we'll need to do a little more to activate that feature.

[edunham]

@aneeshusa I don't think that auto-rebooting would be a good idea right now. Latest commit implements the other 3 changes you suggested.

[edunham]

@bors-servo r? @aneeshusa

[aneeshusa]

Didn't see you had updated this, sorry.

This is going to require some in Vagrant testing - I suspect the unattended-upgrades package has an associated service we'll need to start (due to #229).

[aneeshusa]

I'd prefer to keep this state ID as just python2-dev, and add a new pkg.installed state under the unattended-upgrades ID to install the respective package. That lets us keep all of the unattended upgrades states together.

[aneeshusa]

Also, the new pkg.installed state should require the debconf state for ordering purposes.

[bors-servo]

☔ The latest upstream changes (presumably #577) made this pull request unmergeable. Please resolve the merge conflicts.