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

@@ -7,9 +7,9 @@ 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
+                if [ -x /sbin/chkconfig ] ; then
+                        /sbin/chkconfig --del mysql > /dev/null 2>&1
+                fi
         fi
 fi