Rename `binary` test files in integration suites
Remove source mention in metadata.rb
Install files as root rather than configured user

In certain scenarios `Chef::Config.file_cache_path` is actually a hidden
directory under `/root`, which is not such a good thing when attempting
to copy files as the configured user, so let’s do this as `root` and
preserve most of the attributes as they were when they were extracted.
Revert "Use `/usr/lib/systemd/system` for service file"

This reverts commit 875419b57f9a497df3bf50ce85251e835631338e.
Install Kafka into a version specific directory

To facilitate upgrading a Kafka node it’s somewhat necessary to install
each version into each own directory and then maintain a symlink to the
currently installed version. If there had been an actual package to
install that would’ve simplified things, but alas there’s none at the
moment that’ll cover all supported platforms, so this is the next best
thing.

Furthermore the home directory of the `kafka` user has been changed to
`/var/empty/kafka` rather than the install directory. Why this particular
directory you might ask? Well, I inspected /etc/passwd on CentOS 6.5 and
noticed that some (service) users used /var/empty/<service> as their
home directory, so I thought why not?
Extract variables in `_install` recipe to helpers
Remove comment in `_coordinate` recipe