More manifest cleanup for puppet-lint

New puppet-lint has more crazy lint rules =(
Rename apt-dater, percona-apt (remove dashes)

New puppet-lint doesn't like class names with dashes in them.
networking: add missing EOL to /etc/hosts
validate.py: lint entire modules at a time

New puppet-lint will lint an entire directory if we ask it to, so we
just do that instead of linting individual manifests.

Note that we still need to lint individual modules (rather than the
entire `modules` directory) since we don't want to lint non-OCF modules.