We don't actually need to check the implicit object argument's

We don't actually need to check the implicit object argument's
conversion a second time for a conversion candidate (with the real
acting context), because the only problems we would find are access or
ambiguity issues that won't be diagnosed until we pick this
candidate. Add a test case to prove it to myself.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@111526 91177308-0d34-0410-b5e6-96231b3b80d8