In notifier tests, improve pylint

Make some small improvements to clean up the notifier tests.

- Use pylint symbolic names for disables because they are easier to
  understand when reading.
- Disable no-self-use at the NotifierTest class block level so that
  all tests can be written as methods without lint warnings.
- Fix some long lines
- Shorten test names. These become more readable this way as well.
- Remove unnecessary reassignment of h.notifier classes as test class
  attributes `rtemp` and `ntemp'.