Close PR#16028. Make the sanity check saner. The condition that we

check for on the server may arise legitimately on the client. The
correct way to check for a zero record length is to check for it
without the LAST_FRAG marker in it, since it's legal to send a LAST_FRAG
marker with 0 bytes of data.

PR:		misc/16028

lib/libc/xdr/xdr_rec.c

@@ -558,7 +558,7 @@ set_input_fragment(rstrm)
 	 * but we don't have any way to be certain that they aren't
 	 * what the client actually intended to send us.
 	 */
-	if ((header & (~LAST_FRAG)) == 0)
+	if (header == 0)
 		return(FALSE);
 	rstrm->fbtbc = header & (~LAST_FRAG);
 	return (TRUE);