Dont skip shared file/dir create if the other one is a ghost

Dont skip shared file/dir create if the other one is a ghost

- Explicitly test for shared file/dir being ghost when deciding whether
  to skip create: we must never skip the creation of a real file/dir
  because of a ghost as the ghosts do not get created.
- This fixes the shared ghost testcase, ie the thing that commit
  a712252392eca75443ca45c10a72873cabec7963 was supposed to fix,
  without side-effects that I can see.
(cherry picked from commit 147a26c5f672ee3421fe057725f6be357031bbb5)