Remove dumping of /var/ftd-log/syslog

We likely don't need support for so old systems anymore.
Remove _print_syslog_files_with_header()

The code is now used from a single place, no need to have it as
a function.
Rename _section_syslog -> _dump_logs

Soon this won't be a single section and we don't even have 'syslog' on
some systems.
Write each log file into a separate section