VS integration installer: set SUCCESS=1 if we find VS 2013

Previously we would print an error message on machines where the only VS
version we find is 2013, even though we successfully install the integration
files for it.

Also, we shouldn't have two END labels.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204629 91177308-0d34-0410-b5e6-96231b3b80d8