Make autopush more user friendly

- Tells the user the a push or phone is being called, instead of just hanging
  waiting for a response
- Adds a configuration option to the set the number of attempts a user gets
  to try to log in, useful for autopush because it should probably be set to
  1 or 2 for autopush, rather than 3.
- Displays the enroll link for new users if autopush = yes
- Remove a compiler warning, because that's the thing to do now
- Fix some minor indentation errors
Fix Duo Unix unit tests

The SSL certificates had expired, generated new ones that have a 10 year
expiration date (July 3, 2023)
Update man page for 'tries' configuration option