Fixed a leak of a notification when replying to a conversation

When replying to a child in a group, the notification could get
removed, but forced to stay in the parent. This behavior doesn't
make sense if we're keeping around the notification.

Change-Id: I920eded257726fe8536f769357a5736ebf076051
Fixes: 112714177
Test: add group of 2, reply on child, observe no leak