lib: de-uglify `-t` option + `log stdout` combo

lib: de-uglify `-t` option + `log stdout` combo

The logging code writes log messages with a `\n` line ending, meanwhile
the VTY code switches it so you need `\r\n`...

And we don't flush the newline after executing a command either.

After this patch, starting daemons like `zebra/zebra -t` should provide
a nice development/debugging experience with a VTY open right there on
stdio and `log stdout` interspersed.

(This is already documented in the man pages, it just looked like sh*t
previously since the log messages didn't newline correctly.)

Signed-off-by: David Lamparter <equinox@diac24.net>