Rename of constants in ASTImporterVisibilityTest. NFC.

Reviewers: martong, a.sidorin, shafik

Reviewed By: shafik

Subscribers: shafik, rnkovacs, dkrupp, Szelethus, gamesh411, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D67174

llvm-svn: 371021