Fix the auto-expand-hints logic

Summary:
People were complaining that hints were auto expanding in mastery mode.
While there might be a deeper fix to not do this at all in topic/mastery mode,
the logic is inverted anyways, so it only shows up in the most confusing
states right now.

Test Plan:
open some hints in /math/arithmetic/fractions/understanding_fractions/e/fractions_on_the_number_line_1
reload it, make sure they're auto expanded
reload it in athena as a task, make sure it's auto expanded

Reviewers: james, alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D2468