vfs_streams_xattr: use SMB_VFS_NEXT_OPEN and CLOSE

vfs_streams_xattr: use SMB_VFS_NEXT_OPEN and CLOSE

Using the SMB_VFS_OPEN leads to a recursion in the VFS that is hard to
follow and debug. It's called twice for the same fsp with two different
smb_fname's which makes it at least hard to debug, it may even be an
invalid usage.

Changing this here to use the NEXT function instead should have no
change in behaviour otherwise.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=12565

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Uri Simchoni <uri@samba.org>