rc: kill /var/run/nologin at bootup; #245

Only a workaround.  Need to take this to FreeBSD.

src/etc/rc

@@ -183,6 +183,9 @@ fi
 mkdir -p /var/run /var/log /var/etc /var/db/entropy /var/at/jobs \
     /var/empty /var/tmp
 
+# work around the fact that shutdown(8) doesn't clean up this file
+rm -f /var/run/nologin
+
 # write /var/run/dmesg.boot
 /etc/rc.d/dmesg onestart