When reading the byte from the wait file descriptor failed, jack would mark the client at the head of the external client chain
with an error. But the fault may not have been with that client. So now if the read error is EAGAIN ('no data available') do
not mark the client, but rely on other mechanisms to detect too-slow or dead clients.

Also tweak VERBOSE output a little in some related spots.

This cannot be implemented at present because jack_port_set_name() does not take
a jack_client_t* as an argument, and thus no msg can be sent to the server
regarding the name change. Jack2 accomplishes this by walking its static array
of clients to find one that is in use and sends the msg using that one. This
is not possible in Jack1 because we do not use static arrays of clients (or
ports).