stress-cpu to cpu-stress
stress-cpu to cpu-stress

In four locations in the lab the cpu-stress Docker image is referred to as stress-cpu (including when building the image). This commit changes the stress-cpu references to cpu-stress for consistency with the rest of the lab, including the directory name and docker-compose.yml.
ManoMarks/labs,ManoMarks/labs,ManoMarks/labs,ManoMarks/labs,ManoMarks/labs,ManoMarks/labs,ManoMarks/labs,ManoMarks/labs