Fixed an issue where notifications weren't dismissed properly

Whenever the blocking helper was showing, the notification wasn't
actually dismissed in the notification manager and therefore the
notification dot and other visuals could be wrong as a result.
The reason was that we were lifetime extenders could even trigger
when the notification was dismissed.

Test: atest SystemUITest
Bug: 125799998
Change-Id: Iac7e690f609414de83eefcfeb38623d7668691c3