Add a specific case of EOF on stdin to avoid situations where the
message `error reading from stdio. res=0` is repeated forever if stdin
is not a terminal. When ethos is started as a background process with
stdin redirected to /dev/null, e.g. `ethos ... < /dev/null &`, then
reading stdin will always result in a 0 length read (EOF).
If stdin is a tty we close the program on EOF (CTRL+D in the terminal),
otherwise, we stop reading from stdin after EOF was reached, but
continue tunneling traffic as usual.
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