syslog-ng.inc: fix prerm script & class includes

The order of class includes is very important because it's the order in
which classes are evaluated. Both update-rc.d and update-alternatives
write to the prerm script, so the class order decides the script code
ordering. As they are now, prerm is:

 #!/bin/sh
        update-alternatives --remove  syslog-init /etc/init.d/syslog.syslog-ng
if [ -z "$D" ]; then
        /etc/init.d/syslog stop
fi

This causes errors because when syslog-ng is the only alternative it is
removed and then the script tries to stop it (No such file or directory)
but even if there are other alternatives, the script tries to stop
something other than syslog-ng which was removed.

By reversing the include order, prerm gets generated correctly and it
tries to stop syslog-ng before removing it:

if [ -z "$D" ]; then
        /etc/init.d/syslog stop
fi
update-alternatives --remove  syslog-init /etc/init.d/syslog.syslog-ng

Signed-off-by: Ioan-Adrian Ratiu <adrian.ratiu@ni.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Armin Kuster <akuster808@gmail.com>