check_token was always returning true; now it doesn't.

Notes:
should check for null token.  i'll fix with a follow-on patch
- quanstro


Reference: /n/atom/patch/applied/token-realcheck
Date: Sat Mar 28 05:01:53 CET 2015
Signed-off-by: a@9srv.net
Reviewed-by: quanstro

--- /sys/src/cmd/upas/filterkit/token.c	Sat Mar 28 05:01:01 2015
+++ /sys/src/cmd/upas/filterkit/token.c	Sat Mar 28 05:01:02 2015
@@ -40,7 +40,8 @@
 	buf[i] = 0;
 	now = time(0);
 	for(i = 0; i < 14; i++){
-		if(s = mktoken(key, now-24*60*60*i)){
+		s = mktoken(key, now-24*60*60*i);
+		if(strstr(buf, s) != nil){
 			free(s);
 			return nil;
 		}