clang-format: [JS] Allow top-level conditionals again.

I am not sure exactly which test breakage Martin was trying to fix in
r273694. For now, fix the behavior for top-level conditionals, which
(surprisingly) are actually used somewhat commonly.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@275183 91177308-0d34-0410-b5e6-96231b3b80d8