Docker issues after running pre-written version.

[flyingzardos]

After running the pre-written version, going along with the tutorial, I was unable to create the catalog container. First, the container already existed was an error, then, the ports were already in use was an error. I would suggest creating a script which removes any containers which were created during the first part of the tutorial. Then, when the student/user attempts to create containers, there will be no issues with preexisting containers.