Make FileBackend VCS diff friendly

[sverrehu]

• Please check if the PR fulfills these requirements

• The commit messages are descriptive
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• An issue has been created for the pull requests. Some issues might require previous discussion.

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Increase CI/CD-friendlyness for FileBackend state files. Recent introduction of JSON for state files in JulieOps made it harder to track state changes in git, since the entire JSON was stored as a single line. This patch will pretty-print the JSON text, in order to better be able to track what has changed.

NOTE: This patch is built on top of my previous, unmerged PR.

• What is the current behavior? (You can also link to an open issue here)

.cluster-state is a single line of JSON, so when committing to git, it is impossible (or at least cumbersome) to se what has changed.

• What is the new behavior (if this is a feature change)?

.cluster-state is a pretty-printed, multi-line JSON file.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

I don't think so.

• Other information:

[sverrehu]

I guess the failing test is a transient failure. Integration tests (-Pacls) run fine on my Mac and on my Linux.

[purbon]

@sverrehu I merged the other PR and now this needs rebase. Not sure about the test, I will test as well once conflicts are fixed. thanks a lot again for your help and steady contributions, I am personally sad I can't keep up due to family and work.

Thanks again

[purbon]

so yes, test was transient failure ;-)

[sverrehu]

I tried to fix, but there are unrelated changes in my PR, so I failed. Closing for now. My git-foo is not as strong as my Java-foo.

[sverrehu]

Re "I am personally sad I can't keep up due to family and work"... Yes, I have been there. I'm probably 20 years ahead, and both my kids have moved out. Would like to send you a PM, if I figured out how to do it. shh+github@thathost.com