Only output debug info when in debug mode.

[desrosj]

This adds a conditional statement that checks for debug mode to be enabled before outputting debug information.

Trac ticket: Core-63170.

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[johnbillion]

I'm indifferent about this change to be honest. Sometimes there is value is seeing debug info when a step fails, but I suppose that debug info is unlikely to change when the workflow gets re-run. This change at least standardises the output.

[desrosj]

Workflows runs triggered by push events will always run twice, with debug mode enabled the second time.

But I guess one downfall is that someone outside of the organization opening a pull request will never get to see the debug info because they do not have the required access to rerun a workflow. That could make this undesirable.

I also don't feel strongly on this. It was something I considered as a potential optimization. Let's get a few other opinions.