swifi: various improvements

swifi: various improvements

- no longer inject fewer faults than instructed;
- no longer apply a limit on the number of injected faults;
- refactory to allow for random faults (type 99);
- also allow for stop faults (type 50);
- massive dead code cleanup;
- move outdated test cruft into tests/ subdirectory; it is kept only
  as an example of how to use swifi.

Change-Id: I8a3cb71902dfaadb7bf785723b917307db83d0d5