afs: Fix yfs_fs_fetch_status() to honour vnode selector

Fix yfs_fs_fetch_status() to honour the vnode selector in
op->fetch_status.which as does afs_fs_fetch_status() that allows
afs_do_lookup() to use this as an alternative to the InlineBulkStatus RPC
call if not implemented by the server.

This doesn't matter in the current code as YFS servers always implement
InlineBulkStatus, but a subsequent will call it on YFS servers too in some
circumstances.

Fixes: e49c7b2f

 ("afs: Build an abstraction around an "operation" concept")
Signed-off-by: David Howells <dhowells@redhat.com>