cangen: set seed value for pseudo random numbers

As pointed out by Andre Naujoks the pseudo random generator should be
initialized with a seed to prevend this ugly behaviour:

$ ./cangen vcan2 -v & ./cangen vcan1 -v
[1] 5995
  vcan2  567#69.98.3C.64.73.48
  vcan1  567#69.98.3C.64.73.48
  vcan2  451#4A.94.E8.2A.EC.58.55.62
  vcan1  451#4A.94.E8.2A.EC.58.55.62
  vcan2  729#BA.58.1B.3D.AB.D7.7E.50
  vcan1  729#BA.58.1B.3D.AB.D7.7E.50
(..)

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>

cangen.c

@@ -155,6 +155,11 @@ int main(int argc, char **argv)
 	struct ifreq ifr;
 
 	struct timespec ts;
+	struct timeval now;
+
+	/* set seed value for pseudo random numbers */
+	gettimeofday(&now, NULL);
+	srandom(now.tv_usec);
 
 	signal(SIGTERM, sigterm);
 	signal(SIGHUP, sigterm);