Fix dhcp settings cleanup in Ubuntu 12.04 and higher

[legal90]

There is a typo. It should be /var/lib/dhcp/*, like in the similar script for Debian: https://github.com/chef/bento/blob/250efaa/scripts/debian/networking.sh#L8

[tersmitten]

In Ubuntu 10.04 it used to be dhcp3. But that's probably not a problem :-)

[legal90]

Oh, is it? Sorry, I didn't know about that.
If we care about this case, then I can change my PR by adding some regex there

[tersmitten]

ubuntu-10.04-amd64.json is still in the repository. Let's make sure both cases work :-)

[cheeseplus]

@tersmitten +1- although we'll be moving any deprecated platforms into a separate folder and labeling as such, we definitely want things to still work because folks will for sure continue to use EoL platforms

[legal90]

@cheeseplus Done. I've kept the previous dir name and just added /var/lib/dhcp/*

[cheeseplus]

lgtm