Change syslog.conf comments relating to network logging to focus on client

Change syslog.conf comments relating to network logging to focus on client
setup which is configured in the file itself, rather than talking partly about
client (set in the file), command-line flags used for servers which are
better suited to the syslogd(8) manual, and ISDN.

In the commented-out examples, use tls rather than the plaintext protocol.
If users don't need tls they can change it, but it's a sane default, and
a good place to show that we have the feature.

ok bluhm@