Don't reset the focus to the search line edit twice.

This is now done in a more generic way when switching rooms in the connection between ChannelListView::roomSelected and the widget's roomSelected signal. Don't do it again here for the ctrl-up/down and Enter actions. Also, don't trigger re-selection of the room we are already in apart from in the Enter case, which is supposed to behave like clicking on the channel by mouse (which also re-selects). Make sure that the focus in the Enter case is not on the search line edit before doing the re-selection, as we want the focus to explicitely go to the message line edit and be able to start typing there, matching the semantics of what click selection does.