Add lvm module to Puppetfile

Adds the lvm module forked from Puppet Labs which we can use to
configure lvm volumes from Puppet.

Also updates the sudo module version in Puppetfile.lock.
Configure LVM volume for mirror data

Uses the Puppet LVM module to configure the LVM volume where the mirror
data is stored.
Rename `data_dir` to `mirror_data`

Change `data_dir` to `mirror_data` to make it more meaningful in
context.
Merge pull request #26 from alphagov/63525426-more-repeatable

Configures LVM using Puppet on mirror boxes