cifs: Do not access tcon->cfids->cfid directly from is_path_accessible

cfids will soon keep a list of cached fids so we should not access this
directly from outside of cached_dir.c

Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>