[Mimedefang] Specfile bug: disables service on update

[Kenneth Porter]

I came back from vacation to find MD stopped, apparently due to a power 
failure rebooting the server. More investigation revealed a bug in the spec 
file scriptlets that handle updates:

$ rpm -q --scripts mimedefang
preuninstall scriptlet (through /bin/sh):
/sbin/chkconfig --del mimedefang

Here's the equivalent stuff for Apache, showing how to handle the update 
case:

$ rpm -q --scripts httpd
preuninstall scriptlet (through /bin/sh):
if [ $1 = 0 ]; then
        /sbin/service httpd stop > /dev/null 2>&1
        /sbin/chkconfig --del httpd
fi

(I've removed the irrelevant scriptlets in the output above.)

The initscript symlinks for MD were getting unconditionally deleted on 
update, so the next time the box rebooted, MD didn't start, and that in 
turn prevents sendmail from accepting any mail.