Add ability to override default-host configuration

[dave-pollock]

Pull Request (PR) description

Add ability to override default-host configuration. The default-host configuration is used to control the "host" property which Splunk will use to identify the forwarder. The current behaviour forces the default-host to match the server's $HOSTNAME. In my environment we prefer to customise this name to identify the region and environment for the forwarder (info we don't normally include in the server's hostname).

The default behaviour is maintained so this shouldn't break any existing setup. It just adds the ability to override it if required.

This Pull Request (PR) fixes the following issues

N/A

[dave-pollock]

I don't really see how these test failures could be related to my change?

Please let me know if I'm missing something. Cheers!

[dave-pollock]

@bastelfreak since you seem to be the most active maintainer would you mind reviewing this PR if you have a minute free? Thanks.

[dave-pollock]

@ghoneycutt perhaps you could take a look at this if you have a moment?

[vox-pupuli-tasks]

Dear @dave-pollock, thanks for the PR!

This is Vox Pupuli Tasks, your friendly Vox Pupuli Github Bot. I noticed that your pull request has CI failures. Can you please have a look at the failing CI jobs?
If you need any help, you can reach out to us on our IRC channel voxpupuli on Freenode or our Slack channel voxpupuli at slack.puppet.com.
You can find my sourcecode at voxpupuli/vox-pupuli-tasks

[bastelfreak]

@dave-pollock can you please rebase this against our latest master? The git history is a bit clumsy at the moment.

[dave-pollock]

@bastelfreak I've rebased.