Fix a dangling StringRef bug in the auto upgrader. In one case, we reset

CI's name, and then used the StringRef pointing at its old name. I'm
fixing it by storing the name in a std::string, and hoisting the
renaming logic to happen always. This is nicer anyways as it will allow
the upgraded IR to have the same names as the input IR in more cases.

Another bug found by AddressSanitizer. Woot.

llvm-svn: 160572