clang-format: Simplify and improve stop condition for formatting

unaffected lines with incorrect initial indent.

Starting from:
  namespace {
    int i; // There shouldn't be indentation here.
    int j; // <- call clang-format on this line.
  }

Before:
  namespace {
    int i;
    int j;
    }

After:
  namespace {
    int i;
    int j;
  }

llvm-svn: 251824