[PATCH] Precompute string lengths in PerformRadiusTransaction

Hi, hackers

I noticed that the `PerformRadiusTransaction` function is invoked in a loop, 
and the function itself contains internal loops that repeatedly call strlen() on the 'passwd' and 'secret' strings. 
While the optimization gain may be minimal, I still think it’s worth making the change — 
we can precompute the lengths of these two strings at the start of the function to eliminate redundant strlen() calls.

--
Regards,
Man Zeng
www.openhalo.org