Remove stderr empty check to avoid docker_params_changed failures when warnings appear

[cedws]

Relates to #689.

This is my suggested fix for the docker_params_changed Deferred function in environments where $HOME is unset. This can happen if Puppet is ran as a service. If $HOME is unset, Docker prints this to stderr:

WARNING: Error loading config file: .dockercfg: $HOME is not defined

POSIX spec defines stderr as being for errors and diagnostic information. Therefore any output to stderr does not mean there has been an error. The check as it stands is not correct, so let's check just the status code.

[CLAassistant]

All committers have signed the CLA.

[puppet-community-rangefinder]

docker_params_changed is a function

that may have no external impact to Forge modules.

This module is declared in 6 of 578 indexed public Puppetfiles.

---

These results were generated with Rangefinder, a tool that helps predict the downstream impact of breaking changes to elements used in Puppet modules. You can run this on the command line to get a full report.

Exact matches are those that we can positively identify via namespace and the declaring modules' metadata. Non-namespaced items, such as Puppet 3.x functions, will always be reported as near matches only.

[adrianiurca]

Hey @cedws, thank you for your contribution. I just modified the tests accordingly with your modifications.
For me, this PR looks good!

kind regards,
@adrianiurca

[cedws]

Many thanks for this.