Fix config loading in testcluster plugin
Fix config loading in testcluster plugin

Instructure deprecated Setting.from_config method. I'm doing essentially the same thing as that method did by calling ConfigFile.load now. It gets cached in memory, so there's no hit.
sfu/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,sfu/canvas-lms,grahamb/canvas-lms,grahamb/canvas-lms,va7map/canvas-lms,sfu/canvas-lms,va7map/canvas-lms,sfu/canvas-lms,va7map/canvas-lms,sfu/canvas-lms,va7map/canvas-lms,sfu/canvas-lms