Dress up CAPWAP DoS desc a little.

While the shipping description is fine, it leaves out some details.

Let's make sure the descriptions for modules actually describe the problem, bug, etc. Makes life easier for pentesters when they're writing their reports, not forcing them to do a bunch of reference lookup.

Of course, also need to balance that against copying in description details from VDBs whole cloth. :)

## Verification

 - [x] See that the module description is slightly more useful.

This first came in on #3366 (cross linking here)