MDEV-19706 RPM no longer installs init script on systemd systems, but preun...

MDEV-19706 RPM no longer installs init script on systemd systems, but preun script still tries to erase it

support-files/rpm/server-preun.sh

@@ -7,10 +7,10 @@ if [ $1 = 0 ] ; then
         fi
         if [ -x %{_sysconfdir}/init.d/mysql ] ; then
                 %{_sysconfdir}/init.d/mysql stop > /dev/null
-        fi
                 if [ -x /sbin/chkconfig ] ; then
                         /sbin/chkconfig --del mysql > /dev/null 2>&1
                 fi
+        fi
 fi
 
 # We do not remove the mysql user since it may still own a lot of