[analyzer] Only include uniqueling location as issue_hash when available

This makes us more optimistic when matching reports in a changing code
base. Addresses Jordan's feedback for r171825.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171884 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed