When more than one message is available to read on the ev_sock_
socket, only the first one is read.
Make some changes to be able to read all the messages available by
setting the socket to non-blocking. This way we can detect when
there's nothing left to read and loop back to wait with epoll.
Fix modules starting with no text, but not hidding.
Start with some "text" in the module's label_, update() will then
update it. Since the text should be different, update() will be able
to show or hide the event_box_. This is to work around the case where
the module start with no text, but the the event_box_ is shown.