Simplify, fix and clean up the spec file and related files

[thias]

These are a lot of changes, so feel free to close/ignore and I won't be offended! :smile:

There are many minor things, so I'll just outline the major ones :

• It's now also possible to build from the spec file (using mock for instance).
• The package is noarch, which is more correct and doesn't create any debuginfo by default.
• The extra service.d file was merged into the main unit file.
• The java-headless requirement was added, in order to pull in a JRE if none was present.
• zkcli was moved to /usr/bin.

Let me know if there is anything you dislike or if you have any questions regarding some specific changes.

[embusalacchi]

Any plan to merge this soon?

[id]

@embusalacchi I would like to see the comment about CLASSPATH manupulation to be addressed. Also, there are some conflicts.

[embusalacchi]

I’ve never built an RPM before but I am looking to use this and update the version. I’ll see if I can figure out the classpath changes and submit them for approval. If not I might just try for a zookeeper version update with your original code (which seems to work fine without this PR).