Really fix the load case.

Commit r206510 falsely advertised to fix the load cases, even though it only
fixed the store case. This commit adds the same fix for the load case including
the missing test coverage.

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@206577 91177308-0d34-0410-b5e6-96231b3b80d8