### SOLUTION FOUND ###
So I've found a solution for the problem. Glibc-2.15 was really installed but only libc.so files in /lib64 and /lib32 were updated. Files in /usr/lib64 and /usr/lib32 remained untouched. I don't know the reason for this So I'll mark thread as solved a day or 2 later so that someone would answear this question. All i had to do was:
cp /lib64/libc-2.15.so /usr/lib64/
cp /lib32/libc-2.15.so /usr/lib32/
ln -s /usr/lib64/libc-2.15.so /usr/lib64/libc.so.6
ln -s /usr/lib32/libc-2.15.so /usr/lib32/libc.so.6
At least something like that (written from memory cuz' I'm on different computer now). Thanks for interrest in thread.
EDIT: I guess noone knows answear So i mark this thread as solved.