[MSan] Fix minor issues in testcases (#144073)

Previously,
1. ifaddrs.cpp : mistake `size_t (xxx)` as `sizeof (xxx)`, resulting in
inadequate checks.
2. qsort.cpp : mistake `kSize2` as `kSize1`, resulting in an unexpected
buffer overlow issue.

GitOrigin-RevId: 2796c412499a276ad23ae184daac33175c32424f