clang-format: Fix behavior with comments before conditional expressions

Before:
  SomeFunction(aaaaaaaaaaaaaaaaa,
               // comment.
                   ccccccccccccccccc ? aaaaaaaaaaaaaaaaaaaa
                                     : bbbbbbbbbbbbbbbbbbbb);

After:
  SomeFunction(aaaaaaaaaaaaaaaaa,
               // comment.
               ccccccccccccccccc ? aaaaaaaaaaaaaaaaaaaa : bbbbbbbbbbbbbbbbbbbb);

llvm-svn: 219921