Prevent stacking notifications during rapid toggle

No issue
-Call notifications.closePassive after the resolution of the
 promise that generates the notifications. Otherwise multiple
 promises can stack up after notifications have been cleared,
 which results in a bunch of stacked notifications.
-Remove some unnecessary propagation of rejected promises from
 action handlers that can result in unhandled reject errors.
Merge pull request #3181 from jaswilli/ember-misc

Prevent stacking notifications during rapid toggle