I will wait for Mageia 2 to see if the problem is fixed there.
It isn'i fixed in Mageia 2 I have already checked
The fix I described worked for me on Mageia 1, and I have just tried it out on Mageia 2 (Cauldron) as well. It worked there too.
After you applied it does the front page of webmin say you are running Mageia?
Note that in the edit the character before cat and after /dev/null is a backtick not a single quote. (Yes it makes a difference)
Also use TABS instead of spaces. I am not sure if it is necessary, but all the other lines in the file use TABS.
Installing webmin from the mandriva repositories will not work because the postinstall script will still not recognise your Mageia as a supported OS, although copying the file /usr/share/webmin/mysql/config-mandrake-linux to /etc/webmin/mysql/config will work.