Fix _user_entry_ref_to_path() in chroot

* Add "bool kernel" parameter to vfs_entry_ref_to_path(), so it can be
  specified for which I/O context the entry ref shall be translated.
* _user_entry_ref_to_path(): Use the calling team's I/O context instead
  of the kernel's. Fixes the bug that in a chroot the syscall would
  return a path for outside the chroot.