Make unlink tests pass with goferfs
Make unlink tests pass with goferfs

Required directory checks were being skipped when there was
no child cached. Now the code always loads the child file
before unlinking it.

Updates #1198

PiperOrigin-RevId: 305382323

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor