if there's no whitelist, the address does *not* match.  greylist
processing is gated by the gflag already.

Notes:
Sun Jun 22 17:43:23 EDT 2008 geoff
Tue Nov 18 16:02:45 EST 2008 geoff
    subsumed by nupas.


Reference: /n/sources/patch/sorry/nogreylst
Date: Thu Apr 17 14:37:25 CES 2008
Signed-off-by: quanstro@quanstro.net
Reviewed-by: geoff

--- /sys/src/cmd/upas/smtp/greylist.c	Thu Apr 17 14:35:26 2008
+++ /sys/src/cmd/upas/smtp/greylist.c	Thu Apr 17 14:35:25 2008
@@ -53,7 +53,7 @@
 
 	wl = Bopen(whitelist, OREAD);
 	if (wl == nil)
-		return 1;
+		return 0;
 	while ((line = Brdline(wl, '\n')) != nil) {
 		lnlen = Blinelen(wl);
 		line[lnlen-1] = '\0';		/* clobber newline */