Remove future, add missing notifyDataSetChanged()

This seems to fix a race condition that happens
quite commonly when saving an event modification
or insert.

Nowadays agenda results handling is so heavily
optimised that it doesn't make the UI get stuck.

http://stackoverflow.com/questions/3132021/android-listview-illegalstateexception-the-content-of-the-adapter-has-changed
Cleaner(?)