usr.bin/login: send errors to console if syslog isn't running

I was debugging why login(1) wasn't working as expected on a minimal
MFS_ROOT disk image. This image doesn't have syslogd running so the
warnings were lost and I had to use GDB to find out why login(1) was
failing (missing PAM libraries) instead of being able to see it in
the console output.

MFC after:	1 week
Reviewed By:	pfg
Differential Revision: https://reviews.freebsd.org/D30892

usr.bin/login/login.c

@@ -199,7 +199,7 @@ main(int argc, char *argv[])
 	(void)alarm(timeout);
 	(void)setpriority(PRIO_PROCESS, 0, 0);
 
-	openlog("login", 0, LOG_AUTH);
+	openlog("login", LOG_CONS, LOG_AUTH);
 
 	uid = getuid();
 	euid = geteuid();