[scan-build] fix dead store warnings emitted on clang code base

This fixes dead store warnings of the type "dead assignment" reported
by CLang Static Analyzer on the following file:

- tools/c-index-test/c-index-test.c.

Patch by Apelete Seketeli <apelete@seketeli.net>!

Differential Revision: http://reviews.llvm.org/D19831

llvm-svn: 268453