vfs_ceph: use fsp_get_pathref_fd in ceph fstatat and close vfs calls

vfs_ceph: use fsp_get_pathref_fd in ceph fstatat and close vfs calls

Replace fsp_get_io_fd with fsp_get_pathref_fd as these calls do use
pathref fsps. fsp_get_io_fd asserts that the fsp is not pathref and
asserts (on a debug build) or returns -1 (non debug build).

Prior to these changes running ls on the root of the share failed.
Logging from the failure case:
```
openat_pathref_fsp: smb_fname [.]
openat_pathref_fullname: smb_fname [.]
fsp_new: allocated files structure (1 used)
file_name_hash: //. hash 0x3dfcc1c2
check_reduced_name: check_reduced_name [.] [/]
cephwrap_realpath: [CEPH] realpath(0x55604da9a030, .) = //.
check_reduced_name realpath [.] -> [//.]
check_reduced_name: . reduced to //.
cephwrap_openat: [CEPH] openat(0x55604da9a030, ., 0x55604da81f00, 133120, 0)
cephwrap_openat: [CEPH] open(...) = 10
cephwrap_fstat: fsp_get_io_fd: fsp [.] is a path referencing fsp
[CEPH] fstat(0x55604da9a030, -1)
fsp_get_io_fd: fsp [.] is a path referencing fsp
cephwrap_fstat: [CEPH] fstat(...) = -9
fd_openat: name ., flags = 04000 mode = 00, fd = 10.  NT_STATUS_INVALID_HANDLE
openat_pathref_fullname: Opening pathref for [.] failed: NT_STATUS_INVALID_HANDLE
```

This change also seems to match the recommendations in the `When to use
fsp_get_io_fd() or fsp_get_pathref_fd()` section of The_New_VFS.txt
document.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15307

Signed-off-by: John Mulligan <jmulligan@redhat.com>
Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Gunther Deschner <gdeschne@redhat.com>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Mon Feb 13 20:04:38 UTC 2023 on atb-devel-224