Remove artifacts created in the course of testing

[Sam May (ag-eitilt)]

A number of our tests create files to test visibility, collisions, etc. These have been sticking around after the test is complete and cluttering git status. This PR adds cleanup rms at the end of the relevant tests so that the workspace is left in the same state it started.

Two notes on the implementation:

• None of these files should be critical for debugging errors, if we do wind up regressing one or more of these tests. (If they were, the better solution would be adding them to .gitignore -- as we do for the wake.db and similar which are kept around.)
• We still want to keep the removals of these same files at the beginning of the scripts, in case one of them gets interrupted halfway through and needs cleanup before the next run.