(maint) Fix failing WriteOnlyYaml acceptance test

Without this patch the WriteOnlyYaml acceptance test is failing in
master.  The root cause of this failure is the change in behavior in
30fe09e - (#20284) Output one item per line for arrays in console output

The change in behavior causes the default renderer to print a more human
readable vertical list when the output data from Faces is an array.
This change caused the assumptions made in the WriteOnlyYaml test to no
longer be valid.

The acceptance tests appears to assume JSON output from the `puppet
node` command in order to validate the presence of the expected cached
node data.  This patch changes the test to explicitly render the output
of the command using json to ensure the command produces the output
format the test expects.
(maint) Update branch strategy to be the git flow process

Without this patch it's still a bit confusing how to deal with a bug fix
that is merged into stable.  The merge up process documented in
COMMITTERS requires us to reset the stable branch on a new release.

We can avoid this reset if we switch fully to the process described by
[git flow](http://nvie.com/posts/a-successful-git-branching-model/).
The major difference described in this commit is that bug fixes are
reset onto stable, then merged as-is into both `stable` and `master`
without a merge-up of stable into master or a rebase of the change set
back onto master.

This process avoids the reset, allows both `stable` and `master` to have
infinite lifetimes, and keeps the history clean and free of duplicate
commits.

[ci skip]
Merge branch 'jeffmccune-git_flow'

* jeffmccune-git_flow:
  (maint) Update branch strategy to be the git flow process

closes #1604
[ci skip]
Merge branch 'master' of https://github.com/puppetlabs/puppet