Changing some external testing scripts.

- The absolute path canonifier was overzealously canonifying relevant
  log fields, so it's no longer generally applied to diffing all
  baselines.  I don't think there's any logs that require local
  filesystem path names that aren't already tested by a unit test,
  but if any show up in the future, they can be canonified on a
  case-by-case basis.

- Removed some logs from being diff'd in the diff-all script
  because they're either already covered by a unit test
  (load_scripts.log) or because of difficulty/maintainenance
  tradeoff (prof.log).

Baselines for the external bro-testing repo still need updating.

testing/scripts/diff-canonifier-external

@@ -5,4 +5,3 @@
 `dirname $0`/diff-remove-timestamps \
     | `dirname $0`/diff-remove-uids \
     | `dirname $0`/diff-remove-mime-types \
-    | `dirname $0`/diff-remove-abspath