[CFG] [analyzer] Recall that we only skip NoOp casts in construction contexts.

For now. We should also add support for ConstructorConversion casts as presented
in the attached test case, but this requires more changes because AST around
them seems different.

The check was originally present but was accidentally lost during r326021.

Differential Revision: https://reviews.llvm.org/D43840

llvm-svn: 326402