dracut: 98syslog auto-detect feature

Hello,

I had a look to the dracut syslog module and I've notice that, despite
the code parses the syslog.type argument, it does not actually run
anything but `rsyslogd`.

It's like this since its introduction, the code seems ready to run
`syslogd` or `syslog-ng` but it does not do it.  The
`rsyslogd-start.sh`, despite the name, is written to start any of the
three services, only that at the end it runs only `rsyslogd` (so,
perhaps the name is indeed correct). Then, `syslog-cleanup.sh`
executes the stop service `"${syslogtype}"-stop`, but the only
"*-stop" script available is for rsyslogd.

Am I missing something? If not, I see the following options:

1 clarify that this module supports only "rsyslogd":
1.a by adding "warn" when syslog or syslog-ng are selected
1.b by documenting it
1.c by renaming the module 98rsyslog and removing the auto selection

2 add support for syslog and syslog-ng (even though, nobody complained in 10 years)